Dimensionally stable fast etching glasses

ABSTRACT

Substantially alkali free glasses are disclosed with can be used to produce substrates for flat panel display devices, e.g., active-matrix liquid crystal displays (AMLCDs). The glasses have high annealing temperatures and etch rates. Methods for producing substantially alkali free glasses using a downdraw process (e.g., a fusion process) are also disclosed.

This application is a continuation application of co-pending U.S. application Ser. No. 15/048,492 filed on Feb. 19, 2016 which is a continuation application of U.S. application Ser. No. 14/926,940 filed on Oct. 29, 2015 which claims the benefit of priority to U.S. Provisional Application No. 62/151,741 filed on Apr. 23, 2015 and U.S. Provisional Application No. 62/073,938 filed on Oct. 31, 2014 the content of each are incorporated herein in their entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to display glass. More particularly, embodiments of the present disclosure relate to display glass for active matrix liquid crystal displays.

BACKGROUND

The production of liquid crystal displays, for example, active matrix liquid crystal display devices (AMLCDs) is complex, and the properties of the substrate glass are important. First and foremost, the glass substrates used in the production of AMLCD devices need to have their physical dimensions tightly controlled. The downdraw sheet drawing processes and, in particular, the fusion process described in U.S. Pat. Nos. 3,338,696 and 3,682,609, both to Dockerty, are capable of producing glass sheets that can be used as substrates without requiring costly post-forming finishing operations such as lapping and polishing. Unfortunately, the fusion process places rather severe restrictions on the glass properties, which require relatively high liquidus viscosities.

In the liquid crystal display field, thin film transistors (TFTs) based on poly-crystalline silicon are preferred because of their ability to transport electrons more effectively. Poly-crystalline based silicon transistors (p-Si) are characterized as having a higher mobility than those based on amorphous-silicon based transistors (a-Si). This allows the manufacture of smaller and faster transistors, which ultimately produces brighter and faster displays.

One problem with p-Si based transistors is that their manufacture requires higher process temperatures than those employed in the manufacture of a-Si transistors. These temperatures range from 450° C. to 600° C. compared to the 350° C. peak temperatures employed in the manufacture of a-Si transistors. At these temperatures, most AMLCD glass substrates undergo a process known as compaction. Compaction, also referred to as thermal stability or dimensional change, is an irreversible dimensional change (shrinkage) in the glass substrate due to changes in the glass fictive temperature. “Fictive temperature” is a concept used to indicate the structural state of a glass. Glass that is cooled quickly from a high temperature is said to have a higher fictive temperature because of the “frozen in” higher temperature structure. Glass that is cooled more slowly, or that is annealed by holding for a time near its annealing point, is said to have a lower fictive temperature.

The magnitude of compaction depends both on the process by which a glass is made and the viscoelastic properties of the glass. In the float process for producing sheet products from glass, the glass sheet is cooled relatively slowly from the melt and, thus, “freezes in” a comparatively low temperature structure into the glass. The fusion process, by contrast, results in very rapid quenching of the glass sheet from the melt, and freezes in a comparatively high temperature structure. As a result, a glass produced by the float process may undergo less compaction when compared to glass produced by the fusion process, since the driving force for compaction is the difference between the fictive temperature and the process temperature experienced by the glass during compaction. Thus, it would be desirable to minimize the level of compaction in a glass substrate that is produced by a fusion process as well as other forming processes (e.g., float).

There are two approaches to minimize compaction in glass. The first is to thermally pretreat the glass to create a fictive temperature similar to the one the glass will experience during the p-Si TFT manufacture. There are several difficulties with this approach. First, the multiple heating steps employed during the p-Si TFT manufacture create slightly different fictive temperatures in the glass that cannot be fully compensated for by this pretreatment. Second, the thermal stability of the glass becomes closely linked to the details of the p-Si TFT manufacture, which could mean different pretreatments for different end-users. Finally, pretreatment adds to processing costs and complexity.

Another approach is to slow the rate of strain at the process temperature by increasing the viscosity of the glass. This can be accomplished by raising the viscosity of the glass. The annealing point represents the temperature corresponding to a fixed viscosity for a glass, and thus an increase in annealing point equates to an increase in viscosity at fixed temperature. The challenge with this approach, however, is the production of high annealing point glass that is cost effective. The main factors impacting cost are defects and asset lifetime. In a modern melter coupled to a fusion draw machine, four types of defects are commonly encountered: (1) gaseous inclusions (bubbles or blisters); (2) solid inclusions from refractories or from failure to properly melt the batch; (3) metallic defects consisting largely of platinum; and (4) devitrification products resulting from low liquidus viscosity or excessive devitrification at either end of the isopipe. Glass composition has a disproportionate impact on the rate of melting, and hence on the tendency of a glass to form gaseous or solid defects, and the oxidation state of the glass impacts the tendency to incorporate platinum defects. Devitrification of the glass on the forming mandrel or isopipe, can best be managed by selecting compositions with high liquidus viscosities.

Asset lifetime is determined mostly by the rate of wear or deformation of the various refractory and precious metal components of the melting and forming systems. Recent advances in refractory materials, platinum system design, and isopipe refractories have offered the potential to greatly extend the useful operational lifetime of a melter coupled to a fusion draw machine. As a result, the lifetime-limiting component of a modern fusion draw melting and forming platform is the electrodes used to heat the glass. Tin oxide electrodes corrode slowly over time, and the rate of corrosion is a strong function both of temperature and glass composition. To maximize asset lifetime, it is desirable to identify compositions that reduce the rate of electrode corrosion while maintaining the defect-limiting attributes described above.

As long as the compaction of a glass is below a threshold level, a significant attribute determining the suitability of a glass as a substrate is the variability, or lack thereof, in total pitch of the substrate during the manufacture of the TFT which can cause misalignment of the components of the TFT and result in bad pixels in the final display. This variability is most significantly due to variations in the compaction of the glass, variations in the elastic distortions of the glass under stress applied by the films deposited during the TFT manufacture, and variations in the relaxation of those same stresses during the TFT manufacturing. A glass possessing high dimensional stability will have reduced variability of compaction as well as reduced stress relaxation, and a glass with a high Young's modulus will help reduce the distortions due to film stress. Consequently, a glass possessing both a high modulus and high dimensional stability will minimize total pitch variability during the TFT process, making it an advantaged substrate for these applications.

While total pitch variability is a key attribute for the suitability of a glass composition for use as a TFT backplane, other attributes are also quite significant. After completion of the manufacturing of the TFTs, panel makers thin the display via an acid etch to reduce the thickness and weight of the final display. Consequently, a glass that etches quickly in commercially available acid compositions would allow for more economical thinning of the glass. Similarly, a glass with low density would also help contribute to the desired reduction of weight of the final display.

Accordingly, there is a need in the art for glass compositions with a high Modulus and high dimensional stability while allowing reliable reduction in thickness and other advantageous properties and characteristics.

SUMMARY OF THE CLAIMS

One or more embodiments of the present disclosure are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 68.5-72.0, Al₂O₃ greater than or equal to about 13.0, B₂O₃ less than or equal to about 2.5, MgO 1.0-6.0, CaO 4.0-8.0, SrO less than or equal to about 4.5, BaO less than or equal to about 4.5, such that (MgO+CaO+SrO+BaO)/Al₂O₃ is less than or equal to about 1.6. The glass has an etch index greater than or equal to about 23, an annealing point greater than or equal to about 800° C. and a Modulus greater than 82 GPa.

One or more embodiments are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃ 13.0-14.0, B₂O₃>0-3.0, MgO 0.9-9.0, CaO 5.25-6.5, SrO>0-6.0, BaO 1.0-9.0, the glass substantially free of alkalis and having an etch index >21 μm/mm³. In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-71.0, B₂O₃>0-2.0, MgO 3.5-5.0, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 68.0-70.5, Al₂O₃ 13.0-14.0, B₂O₃>0-3.0, MgO 0.9-9.0, CaO 5.25-11, SrO>0-6.0, BaO 1.0-9.0, wherein the glass substantially free of alkalis and having an etch index >21 μm/mm³. In some embodiments, the glass comprises, in mole percent on an oxide basis. B₂O₃>0-2.0, MgO 3.5-5.0, CaO 5.25-10.0, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 63.0-75.0, Al₂O₃ 13.0-14.0, B₂O₃>0-2.8, MgO 0.9-9.0, CaO 5.25-11, SrO>0-6.0, BaO 1.0-9.0, wherein the glass substantially free of alkalis and having an etch index >21 μm/mm³, In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-72.0, B₂O₃>0-2.0, MgO 3.5-5.0, CaO 5.25-10.0, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments of the disclosure are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 63.0-75.0, Al₂O₃ 13.0-14.0, B₂O₃>0-3.0, MgO 0.9-9.0, CaO 5.25-11, SrO>0-6.0, BaO 3.0-5.4, where the glass substantially free of alkalis and having an etch index >21 μm/mm³. In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-72.0, B₂O₃>0-2.0, MgO 3.5-5.0, CaO 5.25-10.0, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments of the disclosure are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 63.0-75.0, Al₂O₃ 13.0-14.5, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.0-6.5, SrO>0-6.0, BaO 1.0-9.0, the glass substantially free of alkalis, having (MgO+CaO+SrO+BaO)/Al₂O₃ 1.1-1.6 and an etch index >21 μm/mm³. In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-72.0, MgO 3.5-5.0, CaO 5.25-6.5, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃ 13.0-14.0, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.25-6.5, SrO>0-6.0, BaO 1.0-9.0, where the glass substantially free of alkalis and having an etch index >21 μm/mm³. In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-71.0, MgO 3.5-5.0, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃ 13.0-14.1, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.0-6.5, SrO>0-6.0, BaO 3.5-4.0, where the glass substantially free of alkalis and having an etch index >21 μm/mm³. In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-71.0, MgO 3.5-5.0, SrO>0-2.0.

One or more embodiments are directed to glass comprising, in mole percent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃ 13.0-14.0, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.0-6.5, SrO>0-6.0, BaO 1.0-9.0, the sum of CaO and BaO>8.6, where the glass substantially free of alkalis and having an etch index >21 μm/mm³. In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-71.0, MgO 3.5-5.0, SrO>0-2.0, BaO 2.5-4.5.

Additional embodiments of the present disclosure are directed to glass having an annealing temperature greater than or equal to about 785° C.; a density less than or equal to about 2.65 g/cc; a T_(200P) less than or equal to about 1750° C.; a T_(35kP) less than or equal to about 1340° C.; a Young's modulus greater than or equal to about 82 GPa; and an etch index greater than or equal to about 21 μm/mm³ as defined by the equation: −54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO), wherein the glass is substantially free of alkalis. In some embodiments, the glass has one or more of an annealing temperature greater than or equal to about 800° C.; a density less than or equal to about 2.61 g/cc; a T_(200P) less than or equal to about 1700° C.; a T_(35kP) less than or equal to about 1310° C.; and/or an etch index is greater than or equal to about 21 μm/mm³. In various embodiments, the glass comprises one or more of: SiO₂, in mole percent on an oxide basis, in the range 68.1-72.3; Al₂O₃, in mole percent on an oxide basis, in the range 11.0-14.0; B₂O₃, in mole percent on an oxide basis, in the range >0-3.0; MgO, in mole percent on an oxide basis, in the range 1.0-7.2; MgO, in mole percent on an oxide basis, in the range 3.1-5.8; CaO, in mole percent on an oxide basis, in the range 4.1-10.0; CaO, in mole percent on an oxide basis, in the range 4.5-7.4; SrO, in mole percent on an oxide basis, in the range >0-4.2; SrO, in mole percent on an oxide basis, in the range >0-2.0; BaO, in mole percent on an oxide basis, in the range 1.2-4.4; and/or BaO, in mole percent on an oxide basis, in the range 2.6-4.4. In some embodiments, the glass comprises, in mole percent on an oxide basis, SiO₂ 68.0-72.0, B₂O₃ 0.1-3.0 and CaO 5.0-6.5, In one or more embodiments, the glass comprises, in mole percent on an oxide basis, Al₂O₃ 13.0-14.0, B₂O₃ 0.1-3.0 and CaO 5.25-6.0.

Some embodiments of the disclosure are directed to glass that is substantially free of alkalis. The glass comprises, in mol % on an oxide basis, SiO₂ 69.76-71.62, Al₂O₃ 11.03-13.57, B₂O₃ 0-2.99, MgO 3.15-5.84, CaO 4.55-7.35, SrO 0.2-1.99, BaO 2.61-4.41 and ZnO 0-1.0, wherein the ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6 and the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37.

One or more embodiments of the disclosure are directed to glass substantially free of alkalis comprising in mol % on an oxide basis: SiO₂ 68.14-72.29, Al₂O₃ 11.03-14.18, B₂O₃ 0-2.99, MgO 1.09-7.2, CaO 4.12-9.97, SrO 0.2-4.15, BaO 1.26-4.41 and ZnO 0-1.0, wherein the ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6 and the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37.

Some embodiments of the disclosure are directed to glass that is substantially free of alkalis. The glass has a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ in the range of about 1.0 and 1.6, the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37, T(ann)>785° C., density <2.65 g/cc, T(200P)<1750° C., T(35 kP)<1340° C., Young's modulus >82 GPa, and etch index >21 μm/mm³.

Additional embodiments of the disclosure are directed to glass that is substantially free of alkalis wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6, the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37 and the etch index >21 μm/mm³.

In one or more embodiments, glass that is substantially free of alkalis has a (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6, the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37 and a liquidus viscosity >150 kP.

Some embodiments of the disclosure are directed to glass that is substantially free of alkalis wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and about 1.6, an etch index greater than or equal to 21 μm/mm³, T(ann)>800° C. and Young's modulus >82 GPa.

Further embodiments of the disclosure are directed to aluminosilicate glass articles that are substantially free of alkalis. The glass articles have: an annealing temperature greater than or equal to about 795° C.; a density less than or equal to about 2.63 g/cc; a T_(200P) less than or equal to about 1730° C.; a T_(35kP) less than or equal to about 1320° C.; a Young's modulus greater than or equal to about 81.5 GPa; and an etch index greater than or equal to about 23 μm/mm³.

Additional embodiments of the disclosure are directed to aluminosilicate glass articles that are substantially free of alkalis. The articles have: an annealing temperature greater than or equal to about 800° C.; a density less than or equal to about 2.61 g/cc; a T_(200P) less than or equal to about 1710° C.; a T_(35kP) less than or equal to about 1310° C.; a Young's modulus greater than or equal to about 81.2 GPa; and an etch index greater than or equal to about 23 μm/mm³.

Additional embodiments of the disclosure are directed to an object comprising the glass produced by a downdraw sheet fabrication process. Further embodiments are directed to glass produced by the fusion process or variants thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, which are incorporated in and constitute a part of this specification, illustrate several embodiments described below.

FIG. 1 shows a schematic representation of a forming mandrel used to make precision sheet in the fusion draw process;

FIG. 2 shows a cross-sectional view of the forming mandrel of FIG. 1 taken along position 6; and

FIG. 3 shows spectra for 1200° and 1140° C. blackbodies and the transmission spectrum of 0.7 mm thick Eagle XG® amorphous thin-film transistor substrate.

DETAILED DESCRIPTION

Described herein are alkali-free glasses and methods for making the same that possess high annealing points and high Young's moduli, allowing the glasses to possess excellent dimensional stability (i.e., low compaction) during the manufacture of TFTs, reducing variability during the TFT process. Glass with high annealing points can help prevent panel distortion due to compaction/shrinkage during thermal processing subsequent to manufacturing of the glass. Additionally, some embodiments of the present disclosure have high etch rates, allowing for the economical thinning of the backplane, as well as unusually high liquidus viscosities, thus reducing or eliminating the likelihood of devitrification on the relatively cold forming mandrel. As a result of specific details of their composition, exemplary glasses melt to good quality with very low levels of gaseous inclusions, and with minimal erosion to precious metals, refractories, and tin oxide electrode materials.

In one embodiment, the substantially alkali-free glasses can have high annealing points. In some embodiments, the annealing point is greater than about 785° C., 790° C., 795° C. or 800° C. Without being bound by any particular theory of operation, it is believed that such high annealing points result in low rates of relaxation—and hence comparatively small amounts of compaction—for exemplary glasses to be used as backplane substrate in a low-temperature polysilicon process.

In another embodiment, the temperature of exemplary glasses at a viscosity of about 35,000 poise (T_(35k)) is less than or equal to about 1340° C., 1335° C., 1330° C., 1325° C., 1320° C., 1315° C., 1310° C., 1300° C. or 1290° C. In specific embodiments, the glass has a viscosity of about 35,000 poise (T_(35k)) less than about 1310° C. In other embodiments, the temperature of exemplary glasses at a viscosity of about 35,000 poise (T_(35k)) is less than about 1340° C., 1335° C., 1330° C., 1325° C., 1320° C., 1315° C., 1310° C., 1300° C. or 1290° C. In various embodiments, the glass article has a T_(35k) in the range of about 1275° C. to about 1340° C., or in the range of about 1280° C. to about 1315° C.

The liquidus temperature of a glass (T_(liq)) is the temperature above which no crystalline phases can coexist in equilibrium with the glass. In various embodiments, a glass articles has a T_(liq) in the range of about 1180° C. to about 1290° C., or in the range of about 1190° C. to about 1280° C. In another embodiment, the viscosity corresponding to the liquidus temperature of the glass is greater than or equal to about 150,000 poise. In some embodiments, the viscosity corresponding to the liquidus temperature of the glass is greater than or equal to about 175,000 poise, 200,000 poise, 225,000 poise or 250,000 poise.

In another embodiment, an exemplary glass can provide T_(35k)−T_(liq)>0.25T_(35k)−225° C. This ensures minimum tendency to devitrify on the forming mandrel of the fusion process.

In one or more embodiments, the substantially alkali-free glass comprises in mole percent on an oxide basis:

-   -   SiO₂ 60-80     -   Al₂O₃ 5-20     -   B₂O₃ 0-10     -   MgO 0-20     -   CaO 0-20     -   SrO 0-20     -   BaO 0-20     -   ZnO 0-20         where Al₂O₃, MgO, CaO, SrO, BaO represent the mole percents of         the respective oxide components.

In some embodiments, the substantially alkali-free glass comprises in mole percent on an oxide basis:

-   -   SiO₂ 65-75     -   Al₂O₃ 10-15     -   B₂O₃ 0-3.5     -   MgO 0-7.5     -   CaO 4-10     -   SrO 0-5     -   BaO 1-5     -   ZnO 0-5         wherein

1.0≦(MgO+CaO+SrO+BaO)/Al₂O₃<2 and 0<MgO/(MgO+Ca+SrO+BaO)<0.5.

In certain embodiments, the substantially alkali-free glass comprises in mole percent on an oxide basis:

-   -   SiO₂ 67-72     -   Al₂O₃ 11-14     -   B₂O₃ 0-3     -   MgO 3-6     -   CaO 4-8     -   SrO 0-2     -   BaO 2-5     -   ZnO 0-1         wherein

1.0≦(MgO+CaO+SrO+BaO)/Al2O3<1.6 and 0.20<MgO/(MgO+Ca+SrO+BaO)<0.40.

In one embodiment, the glass includes a chemical fining agent. Such fining agents include, but are not limited to, SnO₂, As₂O₃, Sb₂O₃, F, Cl and Br, and in which the concentrations of the chemical fining agents are kept at a level of 0.5 mol % or less. In some embodiments, the chemical fining agent comprises one or more of SnO₂, As₂O₃, Sb₂O₃, F, Cl or Br in a concentration less than or equal to about 0.5 mol %, 0.45 mol %, 0.4 mol %, 0.35 mol %, 0.3 mol % or 0.25 mol %. Chemical fining agents may also include CeO₂, Fe₂O₃, and other oxides of transition metals, such as MnO₂. These oxides may introduce color to the glass via visible absorptions in their final valence state(s) in the glass, and thus their concentration may be at a level of 0.2 mol % or less. In one or more embodiments, the glass composition comprises one or more oxides of transition metals in a concentration less than or equal to about 0.2 mol %, 0.15 mol %, 0.1 mol % or 0.05 mol %. In some embodiments, the glass composition comprises in the range of about 0.01 mol % to about 0.4 mol % of any one or combination of SnO₂, As₂O₃, Sb₂O₃, F, Cl and/or Br. In specific embodiments, the glass composition comprises in the range of about 0.005 mol % to about 0.2 mol % of any one or combination of Fe₂O₃, CeO₂ and/or MnO₂. In some embodiments, As₂O₃ and Sb₂O₃ comprises less than or equal to about 0.005 mol % of the glass composition.

In one embodiment, exemplary glasses are manufactured into sheet via the fusion process. The fusion draw process may result in a pristine, fire-polished glass surface that reduces surface-mediated distortion to high resolution TFT backplanes and color filters. FIG. 1 is a schematic drawing of a forming mandrel, or isopipe, in a non-limiting fusion draw process. FIG. 2 is a schematic cross-section of the isopipe near position 6 in FIG. 1. Glass is introduced from the inlet 1, flows along the bottom of the trough 4 formed by the weir walls 9 to the compression end 2. Glass overflows the weir walls 9 on either side of the isopipe (see FIG. 2), and the two streams of glass join or fuse at the root 10. Edge directors 3 at either end of the isopipe serve to cool the glass and create a thicker strip at the edge called a bead. The bead is pulled down by pulling rolls, hence enabling sheet formation at high viscosity. By adjusting the rate at which sheet is pulled off the isopipe, it is possible to use the fusion draw process to produce a very wide range of thicknesses at a fixed melting rate.

The downdraw sheet drawing processes and, in particular, the fusion process described in U.S. Pat. Nos. 3,338,696 and 3,682,609 (both to Dockerty), which are incorporated by reference, can be used herein. Without being bound by any particular theory of operation, it is believed that the fusion process can produce glass substrates that do not require polishing. Current glass substrate polishing is capable of producing glass substrates having an average surface roughness greater than about 0.5 nm (Ra), as measured by atomic force microscopy. The glass substrates produced by the fusion process have an average surface roughness as measured by atomic force microscopy of less than 0.5 nm. The substrates also have an average internal stress as measured by optical retardation which is less than or equal to 150 psi. Of course, the claims appended herewith should not be so limited to fusion processes as embodiments described herein are equally applicable to other forming processes such as, but not limited to, float forming processes.

In one embodiment, exemplary glasses are manufactured into sheet form using the fusion process. While exemplary glasses are compatible with the fusion process, they may also be manufactured into sheets or other ware through different manufacturing processes. Such processes include slot draw, float, rolling, and other sheet-forming processes known to those skilled in the art.

Relative to these alternative methods for creating sheets of glass, the fusion process as discussed above is capable of creating very thin, very flat, very uniform sheets with a pristine surface. Slot draw also can result in a pristine surface, but due to change in orifice shape over time, accumulation of volatile debris at the orifice-glass interface, and the challenge of creating an orifice to deliver truly flat glass, the dimensional uniformity and surface quality of slot-drawn glass are generally inferior to fusion-drawn glass. The float process is capable of delivering very large, uniform sheets, but the surface is substantially compromised by contact with the float bath on one side, and by exposure to condensation products from the float bath on the other side. This means that float glass must be polished for use in high performance display applications.

The fusion process may involve rapid cooling of the glass from high temperature, resulting in a high fictive temperature T_(f). The fictive temperature can be thought of as representing the discrepancy between the structural state of the glass and the state it would assume if fully relaxed at the temperature of interest. Reheating a glass with a glass transition temperature T_(g) to a process temperature T_(p) such that T_(p)<T_(g)≦T_(f) may be affected by the viscosity of the glass. Since T_(p)<T_(f), the structural state of the glass is out of equilibrium at T_(p), and the glass will spontaneously relax toward a structural state that is in equilibrium at T_(p). The rate of this relaxation scales inversely with the effective viscosity of the glass at T_(p), such that high viscosity results in a slow rate of relaxation, and a low viscosity results in a fast rate of relaxation. The effective viscosity varies inversely with the fictive temperature of the glass, such that a low fictive temperature results in a high viscosity, and a high fictive temperature results in a comparatively low viscosity. Therefore, the rate of relaxation at T_(p) scales directly with the fictive temperature of the glass. A process that introduces a high fictive temperature results in a comparatively high rate of relaxation when the glass is reheated at T_(p).

One means to reduce the rate of relaxation at T_(p) is to increase the viscosity of the glass at that temperature. The annealing point of a glass represents the temperature at which the glass has a viscosity of 10^(13.2) poise. As temperature decreases below the annealing point, the viscosity of the supercooled melt increases. At a fixed temperature below T_(g), a glass with a higher annealing point has a higher viscosity than a glass with a lower annealing point. Therefore, increasing the annealing point may increase the viscosity of a substrate glass at T_(p). Generally, the composition changes necessary to increase the annealing point also increase viscosity at all other temperatures. In a non-limiting embodiment, the fictive temperature of a glass made by the fusion process corresponds to a viscosity of about 10¹¹-10¹² poise, so an increase in annealing point for a fusion-compatible glass generally increases its fictive temperature as well. For a given glass regardless of the forming process, higher fictive temperature results in lower viscosity at temperature below T_(g), and thus increasing fictive temperature works against the viscosity increase that would otherwise be obtained by increasing the annealing point. To have a substantial change in the rate of relaxation at T_(p), it is generally necessary to make relatively large changes in the annealing point. An aspect of exemplary glasses is that it has an annealing point greater than or equal to about 785° C., or 790° C., or 795° C. or 800° C., or 805° C., or 810° C., or 815° C., or in the range of about 796.1° C. to about 818.3° C. Without being bound by any particular theory of operation, it is believed that such high annealing points results in acceptably low rates of thermal relaxation during low-temperature TFT processing, e.g., typical low-temperature polysilicon rapid thermal anneal cycles.

In addition to its impact on fictive temperature, increasing annealing point also increases temperatures throughout the melting and forming system, particularly the temperatures on the isopipe. For example, Eagle XG® glass and Lotus™ glass (Corning Incorporated, Corning, N.Y.) have annealing points that differ by about 50° C., and the temperature at which they are delivered to the isopipe also differ by about 50° C. When held for extended periods of time above about 1310° C., zircon refractory forming the isopipe shows thermal creep, which can be accelerated by the weight of the isopipe itself plus the weight of the glass on the isopipe. A second aspect of exemplary glasses is that their delivery temperatures are less than or equal to about 1350° C., or 1345° C., or 1340° C., or 1335° C., or 1330° C., or 1325° C., or 1320° C., or 1315° C. or 1310° C. Such delivery temperatures may permit extended manufacturing campaigns without a need to replace the isopipe or extend the time between isopipe replacements.

In manufacturing trials of glasses with high annealing points and delivery temperatures below 1350° C. and below 1310° C., it has been found that the glass showed a greater tendency toward devitrification on the root of the isopipe and—especially—the edge directors relative to glasses with lower annealing points. Careful measurement of the temperature profile on the isotope showed that the edge director temperatures were much lower relative to the center root temperature than had been anticipated and is believed to be due to radiative heat loss. The edge directors typically are maintained at a temperature below the center root temperature to ensure that the glass is viscous enough as it leaves the root to put the sheet in between the edge directors under tension, thus maintaining a flat shape. As edge directors are located at either end of the isopipe, the edge directors are difficult to heat, and thus the temperature difference between the center of the root and the edge directors may differ by 50° or more.

While not wishing to be held to theory, it is believed that the increased tendency toward devitirication in the fusion process can be understood in terms of the radiative heat loss of glass as a function of temperature. Fusion is substantially an isothermal process, so glass exits the inlet at a particular viscosity and exits the root at a much higher viscosity, but the actual values for the viscosity are not strongly dependent on the identity of the glass or the temperature of the process. Thus, a glass with a higher annealing point generally requires much higher isopipe temperatures than a glass with a lower annealing point just to match the delivery and exit viscosities. As an example, FIG. 3 shows blackbody spectra corresponding to 1140° C. and 1200° C., approximately the temperature at the root of the isopipe (10 in FIG. 2) for Eagle XG® glass and Lotus™ glass, respectively. The vertical line at about 2.5 μm corresponds approximately with the start of the infrared cut-off, the region in the near infrared through which optical absorption in a borosilicate glass rises very steeply to a high, nearly constant value. At wavelengths shorter than the cut-off wavelength, a glass is sensibly transparent to a wavelength between 300 and 400 nm, the UV cut-off. Between about 300 nm and about 2.5 μm, the 1200° C. blackbody has a greater absolute energy, and a larger fraction of its total energy than the 1140° C. blackbody. Since the glass is sensibly transparent through this wavelength range, the radiative heat loss from a glass at 1200° C. is much greater than that of a glass at 1140° C.

Again, without being bound by any particular theory of operation, it is believed that since radiative heat loss increases with temperature, and since high annealing point glasses generally are formed at higher temperatures than lower annealing point glasses, the temperature difference between the center root and the edge director generally increases with the annealing point of the glass. This may have a direct relationship to the tendency of a glass to form devitrification products on the isopipe or edge directors.

The liquidus temperature of a glass is defined as the highest temperature at which a crystalline phase would appear if a glass were held indefinitely at that temperature. The liquidus viscosity is the viscosity of a glass at the liquidus temperature. To completely avoid devitrification on an isopipe, it may be helpful for the liquidus viscosity to be high enough to ensure that glass is no longer on the isopipe refractory or edge director material at or near the liquidus temperature.

In practice, few alkali-free glasses have liquidus viscosities of the desired magnitude. Experience with substrate glasses suitable for amorphous silicon applications (e.g., Eagle XG® glass) indicated that edge directors could be held continuously at temperatures up to 60° below the liquidus temperature of certain alkali-free glasses. While it was understood that glasses with higher annealing points would require higher forming temperatures, it was not anticipated that the edge directors would be so much cooler relative to the center root temperature. A useful metric for keeping track of this effect is the difference between the delivery temperature onto the isopipe and the liquidus temperature of the glass, T_(liq). In the fusion process, it is generally desirable to deliver glass at about 35,000 poise (T_(35k)). For a particular delivery temperature, it may be useful to make T_(35k)−T_(liq) as large possible, but for an amorphous silicon substrate such as Eagle XG® glass, it is found that extended manufacturing campaigns can be conducted if T_(35k)−T_(liq) is about 80° or more. As temperature increases, T_(35k)−T_(liq) must increase as well, such that for T_(35k) near 1300° C., it may be helpful to have T_(35k)−T_(liq) equal to or greater than about 100° C. The minimum useful value for T_(35k)−T_(liq) varies approximately linearly with temperature from about 1200° C. to about 1320° C., and can be expressed according to equation (1).

Minimum T _(35k) −T _(liq)=0.25T _(35k)−225,  (1)

where all temperatures are in ° C. Thus, one or more embodiments of exemplary glasses has a T_(35k)−T_(liq)>0.25 T_(35k)−225° C.

In addition, the forming process may require glass with a high liquidus viscosity. This is necessary so as to avoid devitrification products at interfaces with glass and to minimize visible devitrification products in the final glass. Thus, for a given glass compatible with fusion for a particular sheet size and thickness, adjusting the process so as to manufacture wider sheet or thicker sheet generally results in lower temperatures at either end of the isopipe. Some embodiments have higher liquidus viscosities to provide greater flexibility for manufacturing via the fusion process. In some embodiments, the liquidus viscosity is greater than or equal to about 150 kP.

In tests of the relationship between liquidus viscosity and subsequent devitrification tendencies in the fusion process, the inventors have surprisingly found that high delivery temperatures, such as those of exemplary glasses, generally require higher liquidus viscosities for long-term production than would be the case for typical AMLCD substrate compositions with lower annealing points. While not wishing to be bound by theory, it is believed that this arises from accelerated rates of crystal growth as temperature increases. Fusion is essentially an isoviscous process, so a more viscous glass at some fixed temperature may be formed by fusion at higher temperature than a less viscous glass. While some degree of undercooling (cooling below the liquidus temperature) can be sustained for extended periods in a glass at lower temperature, crystal growth rates increase with temperature, and thus more viscous glasses grow an equivalent, unacceptable amount of devitrification products in a shorter period of time than less viscous glasses. Depending on where formed, devitrification products can compromise forming stability and introduce visible defects into the final glass.

To be formed by the fusion process, one or more embodiments of the glass compositions have a liquidus viscosity greater than or equal to about 150,000 poises, or 175,000 poises, or 200,000 poises. A surprising result is that throughout the range of exemplary glasses, it is possible to obtain a liquidus temperature low enough, and a viscosity high enough, such that the liquidus viscosity of the glass is unusually high compared to other compositions.

In the glass compositions described herein, SiO₂ serves as the basic glass former. In certain embodiments, the concentration of SiO₂ can be greater than 60 mole percent to provide the glass with a density and chemical durability suitable for a flat panel display glass (e.g., an AMLCD glass), and a liquidus temperature (liquidus viscosity), which allows the glass to be formed by a downdraw process (e.g., a fusion process). In terms of an upper limit, in general, the SiO₂ concentration can be less than or equal to about 80 mole percent to allow batch materials to be melted using conventional, high volume, melting techniques, e.g., Joule melting in a refractory melter. As the concentration of SiO₂ increases, the 200 poise temperature (melting temperature) generally rises. In various applications, the SiO₂ concentration is adjusted so that the glass composition has a melting temperature less than or equal to 1,750° C. In some embodiments, the SiO₂ concentration is in the range of about 63.0 mol % to about 75.0 mol %, or in the range of about 63.0 mol % to about 71.0 mol %, or in the range of about 65.0 mol % to about 73 mol % or in the range of about 67 mol % and 72 mol %, or in the range of about 68.0 to 72.0 mol %, or in the range of about 68.0 mol % to about 71.0 mol %, or in the range of about 68.0 mol % to about 70.5 mol %, or in the range of about 68.1 mol % to about 72.3 mol %, or in the range of about 68.5 to about 72.0 mol %, or in the range of about 68.95 mol % to about 71.12 mol %, or in the range of about 69.7 to about 71.7 mol %.

Al₂O₃ is another glass former used to make the glasses described herein. An Al₂O₃ concentration greater than or equal to 10 mole percent provides the glass with a low liquidus temperature and high viscosity, resulting in a high liquidus viscosity. The use of at least 10 mole percent Al₂O₃ also improves the glass's annealing point and modulus. In order that the ratio (MgO+CaO+SrO+BaO)/Al₂O₃ is greater than or equal to 1.0, the Al₂O₃ concentration may be below about 15 mole percent. In some embodiments, the Al₂O₃ concentration is in the range of about 11.0 and 14.0 mole percent, or in the range of about 11.0 to about 13.6 mol %, or in the range of about 13.0 mol % to about 14.5 mol %, or in the range of about 13.0 mol % to about 14.0 mol %, or in the range of about 13.0 mol % to about 14.18 mol %. In some embodiments, the Al₂O₃ concentration is greater than or equal to about 9.5 mol %, 10.0 mol %, 10.5 mol %, 11.0 mol %, 11.5 mol %, 12.0 mol %, 12.5 mol % or 13.0 mol % while maintaining a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ greater than or equal to about 1.0.

Some embodiments of the disclosure have a modulus greater than about 81 GPa, or 81.5 GPa, or 82 GPa, or 82.5 GPa, or 83 GPa, or 83.5 GPa, or 84 GPa, or 84.5 GPa or 85 GPa. In various embodiments, an aluminosilicate glass article has a Young's modulus in the range of about 81 GPa to about 88 GPa, or in the range of about 81.5 GPa to about 85 GPa, or in the range of about 82 GPa to about 84.5 GPa.

The density of some embodiments of aluminosilicate glass articles is less than about 2.7 g/cc, or 2.65 g/cc, or 2.61 g/cc, or 2.6 g/cc, or 2.55 g/cc. In various embodiments, the density is in the range of about 2.55 g/cc to about 2.65 g/cc, or in the range of about 2.57 g/cc to about 2.626 g/cc.

B₂O₃ is both a glass former and a flux that aids melting and lowers the melting temperature. It has an impact on both liquidus temperature and viscosity. Increasing B₂O₃ can be used to increase the liquidus viscosity of a glass. To achieve these effects, the glass compositions of one or more embodiments may have B₂O₃ concentrations that are equal to or greater than 0.1 mole percent. As discussed above with regard to SiO₂, glass durability is very important for LCD applications. Durability can be controlled somewhat by elevated concentrations of alkaline earth oxides, and significantly reduced by elevated B₂O₃ content. Annealing point decreases as B₂O₃ increases, so it may be helpful to keep B₂O₃ content low relative to its typical concentration in amorphous silicon substrates. Thus in some embodiments, the glass composition has B₂O₃ concentrations that are in the range of about 0.0 and 3.0 mole percent, or greater than 0 to about 3.0 mol %, or about 0.0 to about 2.8 mol %, or greater than 0 to about 2.8 mol %, or about 0.0 to about 2.5 mol %, or greater than 0 to about 2.5 mol %, or in the range of about 0.0 to about 2.0 mol %, or greater than 0 to about 2.0 mol percent, or in the range of about 0.1 mol % to about 3.0 mol %, or in the range of about 0.75 mol % to about 2.13 mol %.

The Al₂O₃ and B₂O₃ concentrations can be selected as a pair to increase annealing point, increase modulus, improve durability, reduce density, and reduce the coefficient of thermal expansion (CTE), while maintaining the melting and forming properties of the glass.

For example, an increase in B₂O₃ and a corresponding decrease in Al₂O₃ can be helpful in obtaining a lower density and CTE, while an increase in Al₂O₃ and a corresponding decrease in B₂O₃ can be helpful in increasing annealing point, modulus, and durability, provided that the increase in Al₂O₃ does not reduce the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio below about 1.0. For (MgO+CaO+SrO+BaO)/Al₂O₃ ratios below about 1.0, it may be difficult or impossible to remove gaseous inclusions from the glass due to late-stage melting of the silica raw material. Furthermore, when (MgO+CaO+SrO+BaO)/Al₂O₃≦1.05, mullite, an aluminosilicate crystal, can appear as a liquidus phase. Once mullite is present as a liquidus phase, the composition sensitivity of liquidus increases considerably, and mullite devitrification products both grow very quickly and are very difficult to remove once established. Thus, in some embodiments, the glass composition has (MgO+CaO+SrO+BaO)/Al₂O₃≧1.0 (or greater than or equal to about 1.0). In various embodiments, the glass has (MgO+CaO+SrO+BaO)/Al₂O₃≧1.05 (or greater than or equal to about 1.05), or in the range of about 1 to about 1.17.

In one or more embodiments, glasses for use in AMLCD applications have coefficients of thermal expansion (CTEs) (22-300° C.) in the range of about 28×10⁻⁷/° C. to about 42×10⁻⁷/° C., or in the range of about 30×10⁻⁷/° C. to about 40×10⁻⁷/° C., or in the range of about 32×10⁻⁷/° C. to about 38×10⁻⁷/° C.

In addition to the glass formers (SiO₂, Al₂O₃, and B₂O₃), the glasses described herein also include alkaline earth oxides. In one embodiment, at least three alkaline earth oxides are part of the glass composition, e.g., MgO, CaO, and BaO, and, optionally, SrO. The alkaline earth oxides provide the glass with various properties important to melting, fining, forming, and ultimate use. Accordingly, to improve glass performance in these regards, in one embodiment, the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio is greater than or equal to about 1.0. As this ratio increases, viscosity tends to increase more strongly than liquidus temperature, and thus it is increasingly difficult to obtain suitably high values for T_(35k)−T_(liq). Thus in another embodiment, ratio (MgO+CaO+SrO+BaO)/Al₂O₃ is less than or equal to about 2. In some embodiments, the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio is in the range of about 1 to about 1.2, or in the range of about 1 to about 1.16, or in the range of about 1.1 to about 1.6. In detailed embodiments, the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio less than about 1.7, or 1.6, or 1.5.

For certain embodiments of this disclosure, the alkaline earth oxides may be treated as what is in effect a single compositional component. This is because their impact upon viscoelastic properties, liquidus temperatures and liquidus phase relationships are qualitatively more similar to one another than they are to the glass forming oxides SiO₂, Al₂O₃ and B₂O₃. However, the alkaline earth oxides CaO, SrO and BaO can form feldspar minerals, notably anorthite (CaAl₂Si₂O₈) and celsian (BaAl₂Si₂O₈) and strontium-bearing solid solutions of same, but MgO does not participate in these crystals to a significant degree. Therefore, when a feldspar crystal is already the liquidus phase, a superaddition of MgO may serves to stabilize the liquid relative to the crystal and thus lower the liquidus temperature. At the same time, the viscosity curve typically becomes steeper, reducing melting temperatures while having little or no impact on low-temperature viscosities.

The inventors have found that the addition of small amounts of MgO may benefit melting by reducing melting temperatures, forming by reducing liquidus temperatures and increasing liquidus viscosity, while preserving high annealing point and, thus, low compaction. In various embodiments, the glass composition comprises MgO in an amount in the range of about 0.9 mol % to about 9 mol %, or in the range of about 1.0 mol % to about 7.2 mol %, or in the range of about 1.0 mol % to about 6.0 mol %, or in the range of about 2.1 mol % to about 5.68 mol %, or in the range of about 3.1 mol % to about 5.9 mol %, or in the range of about 3.5 mol % to about 5.0 mol %.

The inventors have surprisingly found that glasses with suitably high values of T_(35k)−T_(liq), the ratio of MgO to the other alkaline earths, MgO/(MgO+CaO+SrO+BaO), falls within a relatively narrow range. As noted above, additions of MgO can destabilize feldspar minerals, and thus stabilize the liquid and lower liquidus temperature. However, once MgO reaches a certain level, mullite, Al₆Si₂O₁₃, may be stabilized, thus increasing the liquidus temperature and reducing the liquidus viscosity. Moreover, higher concentrations of MgO tend to decrease the viscosity of the liquid, and thus even if the liquidus viscosity remains unchanged by addition of MgO, it will eventually be the case that the liquidus viscosity will decrease. Thus in another embodiment, 0.20≦MgO/(MgO+CaO+SrO+BaO)≦0.40 or in some embodiments, 0.22≦MgO/(MgO+CaO+SrO+BaO)≦0.37. Within these ranges, MgO may be varied relative to the glass formers and the other alkaline earth oxides to maximize the value of T_(35k)−T_(liq) consistent with obtaining other desired properties.

Without being bound by any particular theory of operation, it is believed that calcium oxide present in the glass composition can produce low liquidus temperatures (high liquidus viscosities), high annealing points and moduli, and CTE's in the most desired ranges for flat panel applications, specifically, AMLCD applications. It also contributes favorably to chemical durability, and compared to other alkaline earth oxides, it is relatively inexpensive as a batch material. However, at high concentrations, CaO increases the density and CTE. Furthermore, at sufficiently low SiO₂ concentrations, CaO may stabilize anorthite, thus decreasing liquidus viscosity. Accordingly, in one or more embodiment, the CaO concentration can be greater than or equal to 4 mole percent, or 4.0 mol %. In various embodiments, the CaO concentration of the glass composition is in the range of about 4.0 mol % to about 8.0 mol %, or in the range of about 4.1 mol % to about 10 mol % (or 10.0 mol %), or in the range of about 4.12 mol % to about 7.45 mol %, or in the range of about 4.5 mol % to about 7.4 mol %, or in the range of about 5.0 mol % to about 6.5 mol %, or in the range of about 5.25 mol % to about 11 mol % (or 11.0 mol %), or in the range of about 5.25 mol % to about 10 mol % (or 10.0 mol %), or in the range of about 5.25 mol % to about 6.5 mol %, or in the range of about 5.25 mol % to about 6.0 mol %.

SrO and BaO can both contribute to low liquidus temperatures (high liquidus viscosities) and, thus, the glasses described herein will typically contain at least both of these oxides. However, the selection and concentration of these oxides are selected to avoid an increase in CTE and density and a decrease in modulus and annealing point. The relative proportions of SrO and BaO can be balanced so as to obtain a suitable combination of physical properties and liquidus viscosity such that the glass can be formed by a downdraw process. In various embodiments, the glass comprises SrO in the range of about 0 to about 6.0 mol %, or greater than 0 to about 6.0 mol %, or about 0 to about 4.5 mol %, 4.2 mol %, or 2.0 mol %, or greater than 0 to about 4.5 mol %, 4.2 mol % or 2.0 mol %, or in the range of about 0.45 mol % to about 4.15 mol %. In some embodiments, the minimum amount of SrO is about 0.02 mol %. In one or more embodiments, the glass comprises BaO in the range of about 0 to about 4.5 mol %, or greater than 0 to about 4.5 mol %, or about 1.0 to about 9.0 mol %, or about 1.2 mol % to about 4.4 mol %, or about 2.42 mol % to about 4.3 mol %, or about 2.5 mol % to about 4.5 mol %, or about 2.6 mol % to about 4.4 mol %, or about 3.0 mol % to about 5.4 mol %, or about 3.5 mol % to about 4.0 mol %.

To summarize the effects/roles of the central components of the glasses of the disclosure, SiO₂ is the basic glass former. Al₂O₃ and B₂O₃ are also glass formers and can be selected as a pair with, for example, an increase in B₂O₃ and a corresponding decrease in Al₂O₃ being used to obtain a lower density and CTE, while an increase in Al₂O₃ and a corresponding decrease in B₂O₃ being used in increasing annealing point, modulus, and durability, provided that the increase in Al₂O₃ does not reduce the RO/Al₂O₃ ratio below about 1.0, where RO═(MgO+CaO+SrO+BaO). If the ratio goes too low, meltability is compromised, i.e., the melting temperature becomes too high. B₂O₃ can be used to bring the melting temperature down, but high levels of B₂O₃ compromise annealing point.

In addition to meltability and annealing point considerations, for AMLCD applications, the CTE of the glass should be compatible with that of silicon. To achieve such CTE values, exemplary glasses can control the RO content of the glass. For a given Al₂O₃ content, controlling the RO content corresponds to controlling the RO/Al₂O₃ ratio. In practice, glasses having suitable CTE's are produced if the RO/Al₂O₃ ratio is below about 1.6.

On top of these considerations, the glasses are preferably formable by a downdraw process, e.g., a fusion process, which means that the glass' liquidus viscosity needs to be relatively high. Individual alkaline earths play an important role in this regard since they can destabilize the crystalline phases that would otherwise form. BaO and SrO are particularly effective in controlling the liquidus viscosity and are included in exemplary glasses for at least this purpose. As illustrated in the examples presented below, various combinations of the alkaline earths will produce glasses having high liquidus viscosities, with the total of the alkaline earths satisfying the RO/Al₂O₃ ratio constraints needed to achieve low melting temperatures, high annealing points, and suitable CTE's. In some embodiments, the liquidus viscosity is greater than or equal to about 150 kP.

In addition to the above components, the glass compositions described herein can include various other oxides to adjust various physical, melting, fining, and forming attributes of the glasses. Examples of such other oxides include, but are not limited to, TiO₂, MnO, Fe₂O₃, ZnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, Y₂O₃, La₂O₃ and CeO₂ as well as other rare earth oxides and phosphates. In one embodiment, the amount of each of these oxides can be less than or equal to 2.0 mole percent, and their total combined concentration can be less than or equal to 5.0 mole percent. In some embodiments, the glass composition comprises ZnO in an amount in the range of about 0 to about 1.5 mol %, or about 0 to about 1.0 mol %. The glass compositions described herein can also include various contaminants associated with batch materials and/or introduced into the glass by the melting, fining, and/or forming equipment used to produce the glass, particularly Fe₂O₂ and ZrO₂. The glasses can also contain SnO₂ either as a result of Joule melting using tin-oxide electrodes and/or through the batching of tin containing materials, e.g., SnO₂, SnO, SnCO₃, SnC₂O₂, etc.

The glass compositions are generally alkali free; however, the glasses can contain some alkali contaminants. In the case of AMLCD applications, it is desirable to keep the alkali levels below 0.1 mole percent to avoid having a negative impact on thin film transistor (TFT) performance through diffusion of alkali ions from the glass into the silicon of the TFT. As used herein, an “alkali-free glass” is a glass having a total alkali concentration which is less than or equal to 0.1 mole percent, where the total alkali concentration is the sum of the Na₂O, K₂O, and Li₂O concentrations. In one embodiment, the total alkali concentration is less than or equal to 0.1 mole percent.

As discussed above, (MgO+CaO+SrO+BaO)/Al₂O₃ ratios greater than or equal to 1.0 improve fining, i.e., the removal of gaseous inclusions from the melted batch materials. This improvement allows for the use of more environmentally friendly fining packages. For example, on an oxide basis, the glass compositions described herein can have one or more or all of the following compositional characteristics: (i) an As₂O₃ concentration of at most 0.05 mole percent; (ii) an Sb₂O₃ concentration of at most 0.05 mole percent; (iii) a SnO₂ concentration of at most 0.25 mole percent.

As₂O₃ is an effective high temperature fining agent for AMLCD glasses, and in some embodiments described herein, As₂O₃ is used for fining because of its superior fining properties. However, As₂O₃ is poisonous and requires special handling during the glass manufacturing process. Accordingly, in certain embodiments, fining is performed without the use of substantial amounts of As₂O₃, i.e., the finished glass has at most 0.05 mole percent As₂O₃. In one embodiment, no As₂O₃ is purposely used in the fining of the glass. In such cases, the finished glass will typically have at most 0.005 mole percent As₂O₃ as a result of contaminants present in the batch materials and/or the equipment used to melt the batch materials.

Although not as toxic as As₂O₃, Sb₂O₃ is also poisonous and requires special handling. In addition, Sb₂O₃ raises the density, raises the CTE, and lowers the annealing point in comparison to glasses that use As₂O₃ or SnO₂ as a fining agent. Accordingly, in certain embodiments, fining is performed without the use of substantial amounts of Sb₂O₃, i.e., the finished glass has at most 0.05 mole percent Sb₂O₃. In another embodiment, no Sb₂O₃ is purposely used in the fining of the glass. In such cases, the finished glass will typically have at most 0.005 mole percent Sb₂O₃ as a result of contaminants present in the batch materials and/or the equipment used to melt the batch materials.

Compared to As₂O₃ and Sb₂O₃ fining, tin fining (i.e., SnO₂ fining) is less effective, but SnO₂ is a ubiquitous material that has no known hazardous properties. Also, for many years, SnO₂ has been a component of AMLCD glasses through the use of tin oxide electrodes in the Joule melting of the batch materials for such glasses. The presence of SnO₂ in AMLCD glasses has not resulted in any known adverse effects in the use of these glasses in the manufacture of liquid crystal displays. However, high concentrations of SnO₂ are not preferred as this can result in the formation of crystalline defects in AMLCD glasses. In one embodiment, the concentration of SnO₂ in the finished glass is less than or equal to 0.25 mole percent.

In some embodiments, it was unexpectedly discovered that higher viscosity glasses described herein can allow a higher concentration of SnO₂ without resulting in any deleterious effects to the glass. For example, conventional wisdom would inform one that a glass having a high annealing point results in a high melting temperature. Such high melting temperatures can result in a worse inclusion quality in the respective glass. To address such inclusion quality, finers can be added; however, glasses having a low viscosity generally do not permit the addition of SnO₂ due to crystallization thereof in the glass. Exemplary glasses, as described herein, however, can possess a higher viscosity resulting in higher forming temperatures and thus allowing a greater concentration of fining agent to be added to the glass thereby resulting in less inclusions. Simply put, it was discovered that by varying the composition of an exemplary glass to create a higher process temperature, a greater amount of fining agent could be added to remove inclusions before crystallization occurred. Thus, an exemplary glass can include SnO₂ at a concentration of between 0.001 mol % and 0.5 mol % and a T₃₅₀ greater than or equal to about 1270° C., greater than or equal to about 1280° C., or greater than or equal to about 1290° C. Another exemplary glass can include SnO₂ at a concentration of between 0.001 mol % and 0.5 mol % and a T_(200P) greater than or equal to about 1650° C., greater than or equal to about 1660° C., or greater than or equal to about 1670° C. Another exemplary glass can include SnO₂ at a concentration of between 0.001 mol % and 0.5 mol % and a T_(35kP) greater than or equal to about 1270° C., greater than or equal to about 1280° C., or greater than or equal to about 1290° C. as well as a T_(200P) greater than or equal to about 1650° C., greater than or equal to about 1660° C., or greater than or equal to about 1670° C. Further exemplary glasses can include SnO₂ at a concentration of between 0.001 mol % and 0.5 mol % and a liquidus temperature of greater than about 1150° C., greater than about 1165° C., or greater than about 1170° C. Such a glass can also have T_(35kP) and/or T_(200P) as discussed above. Of course, SnO₂ can be provided to the glass as a result of Joule melting using tin-oxide electrodes and/or through the batching of tin containing materials, e.g., SnO₂, SnO, SnCO₃, SnC₂O₂, etc.

Tin fining can be used alone or in combination with other fining techniques if desired. For example, tin fining can be combined with halide fining, e.g., bromine fining. Other possible combinations include, but are not limited to, tin fining plus sulfate, sulfide, cerium oxide, mechanical bubbling, and/or vacuum fining. It is contemplated that these other fining techniques can be used alone. In certain embodiments, maintaining the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio and individual alkaline earth concentrations within the ranges discussed above makes the fining process easier to perform and more effective.

The glasses described herein can be manufactured using various techniques known in the art. In one embodiment, the glasses are made using a downdraw process such as, for example, a fusion downdraw process. In one embodiment, described herein is a method for producing an alkali-free glass sheet by a downdraw process comprising selecting, melting, and fining batch materials so that the glass making up the sheets comprises SiO₂, Al₂O₃, B₂O₃, MgO, CaO and BaO, and, on an oxide basis, comprises: (i) a (MgO+CaO+SrO+BaO)/Al₂O₃ ratio greater than or equal to 1.0; (ii) a MgO content greater than or equal to 3.0 mole percent; (iii) a CaO content greater than or equal to 4.0 mole percent; and (iv) a BaO content greater than or equal to 1.0 mole percent, wherein: (a) the fining is performed without the use of substantial amounts of arsenic (and, optionally, without the use of substantial amounts of antimony); and (b) a population of 50 sequential glass sheets produced by the downdraw process from the melted and fined batch materials has an average gaseous inclusion level of less than 0.10 gaseous inclusions/cubic centimeter, where each sheet in the population has a volume of at least 500 cubic centimeters.

U.S. Pat. No. 5,785,726 (Dorfeld et al.), U.S. Pat. No. 6,128,924 (Bange et al.), U.S. Pat. No. 5,824,127 (Bange et al.), and U.S. Pat. Nos. 7,628,038 and 7,628,039 (De Angelis, et al.) disclose processes for manufacturing arsenic free glasses. U.S. Pat. No. 7,696,113 (Ellison) discloses a process for manufacturing arsenic- and antimony-free glass using iron and tin to minimize gaseous inclusions.

According to one embodiment, a population of 50 sequential glass sheets produced by the downdraw process from the melted and fined batch materials has an average gaseous inclusion level of less than 0.05 gaseous inclusions/cubic centimeter, where each sheet in the population has a volume of at least 500 cubic centimeters.

The etch rate of the glass composition is a measure of how quickly a material can be removed from the glass and a rapid etch rate has been found to provide value to panel makers. The inventors have identified an “etch index” which allows one to estimate the etch rate of a glass composition in commercially relevant etching processes (such as, but not limited to, a ten minute soak in a 10% HF/5% HCl solution at 30° C.). This etch index is defined by equation (2)

Etch index=−54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO)   (2)

where the oxides are in mol %. In some embodiments, the etch index is greater than or equal to about 21. In various embodiments, the etch index is greater than or equal to about 21.5, 22, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5 or 31.

Some embodiments of the present disclosure are directed to a glass composition comprising, in mol % on an oxide basis in the ranges:

-   -   SiO₂ 68.5-72.0     -   Al₂O₃≧13.0     -   B₂O₃≦2.5     -   MgO 1.0-6.0     -   CaO 4.0-8.0     -   SrO≦4.5     -   BaO≦4.5         wherein

1.0≦(MgO+CaO+SrO+BaO)/Al₂O₃≦1.6,

an etch index ≧21;

an annealing point ≧800° C.; and

a Modulus >82 GPa.

One or more embodiments of the present disclosure is directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 63.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-3.0     -   MgO 0.9-9.0     -   CaO 5.25-6.5     -   SrO>0-6.0     -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.25-6.5     -   SrO>0-2.0     -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-70.5     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-3.0     -   MgO 0.9-9.0     -   CaO 5.25-11     -   SrO>0-6.0     -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-70.5     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.25-10.0     -   SrO>0-2.0     -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 63.0-75.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.8     -   MgO 0.9-9.0     -   CaO 5.25-1.1     -   SrO>0-6.0     -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-72.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.25-10.0     -   SrO>0-2.0     -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 63.0-75.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-3.0     -   MgO 0.9-9.0     -   CaO 5.25-11     -   SrO>0-6.0     -   BaO 3.0-5.4.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-72.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.25-10.0     -   SrO>0-2.0     -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 63.0-75.0     -   Al₂O₃ 13.0-14.5     -   B₂O₃>0-2.0     -   MgO 0.9-9.0     -   CaO 5.0-6.5     -   SrO>0-6.0     -   BaO 1.0-9.0,         having (MgO+CaO+SrO+BaO)/Al₂O₃ 1.1-1.6

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-72.0     -   Al₂O₃ 13.0-14.5     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.25-6.5     -   SrO>0-2.0     -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 63.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 0.9-9.0     -   CaO 5.25-6.5     -   SrO>0-6.0     -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.25-6.5     -   SrO>0-2.0     -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 63.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 0.9-9.0     -   CaO 5.0-6.5     -   SrO>0-6.0     -   BaO 3.5-4.0.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.0-6.5     -   SrO>0-2.0     -   BaO 3.5-4.0.

Some embodiments of the present disclosure are directed to a substantially alkali free glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 63.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 0.9-9.0     -   CaO 5.0-6.5     -   SrO>0-6.0     -   BaO 1.0-9.0,         wherein the sum of CaO and BaO>8.6.

Some embodiments of the present disclosure are directed to glass comprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-71.0     -   Al₂O₃ 13.0-14.0     -   B₂O₃>0-2.0     -   MgO 3.5-5.0     -   CaO 5.0-6.5     -   SrO>0-2.0     -   BaO 2.5-4.5.

One or more embodiments of the present disclosure are directed to substantially alkali free glass having an annealing temperature greater than or equal to about 785° C.; a density less than or equal to about 2.65 g/cc; a T_(200P) less than or equal to about 1750° C.; a T_(35kP) less than or equal to about 1340° C.; a Young's modulus greater than or equal to about 82 GPa; and an etch index in 10% HF/HCl greater than or equal to about 17.3 μm/mm³, In a detailed embodiment, the glass has an annealing temperature greater than or equal to about 800° C.; a density less than or equal to about 2.61 g/cc; a T_(200P) less than or equal to about 1700° C.; a T_(35kP) less than or equal to about 1310° C.; and an etch index greater than or equal to about 18.5 μm/mm³, In some embodiments, the glass article has a T_(200P) less than or equal to about 1740° C., or 1730° C., or 1720° C., or 1710° C., or 1700° C., or 1690° C., 1680° C., 1670° C., 1660° C. or 1650° C. In one or more embodiments, the glass article has a T_(200P) in the range of about 1640° C. to about 1705° C., or in the range of about 1646° C. to about 1702° C., or in the range of about 1650° C. to about 1700° C.

One or more embodiments of the present disclosure are directed to substantially alkali free glass having one or more of: an annealing temperature greater than or equal to about 785° C.; a density less than or equal to about 2.65 g/cc; a T_(200P) less than or equal to about 1750° C.; a T_(35kP) less than or equal to about 1340° C.; a Young's modulus greater than or equal to about 82 GPa; or an etch index in 10% HF/HCl greater than or equal to about 17.3 μm/mm³. In some embodiments, the glass has one or more of: an annealing temperature greater than or equal to about 800° C.; a density less than or equal to about 2.61 g/cc; a T_(200P) less than or equal to about 1700° C.; a T_(35kP) less than or equal to about 1310° C.; or an etch index greater than or equal to about 18.5 μm/mm³.

One or more embodiments of the disclosure are directed to glass substantially free of alkalis comprising in mol % on an oxide basis,

-   -   SiO₂ 69.76-71.62     -   Al₂O₃ 11.03-13.57     -   B₂O₃ 0-2.99     -   MgO 3.15-5.84     -   CaO 4.55-7.35     -   SrO 0.2-1.99     -   BaO 2.61-4.41     -   ZnO 0-1.0,         wherein the glass has a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ is in         the range of about 1.0 and 1.6 and the ratio of         MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37. In         various embodiments, the glass has one or more of: a T(ann)>785°         C.; a density <2.65 g/cc; a T(_(200P))<1750° C.; a         T_((35kP))<1340° C.; a Young's modulus >82 GPa; or an etch index         >21.

Some embodiments of the disclosure are directed to glass substantially free of alkalis comprising in mol % on an oxide basis,

-   -   SiO₂ 68.14-72.29     -   Al₂O₃ 11.03-14.18     -   B₂O₃ 0-2.99     -   MgO 1.09-7.2     -   CaO 4.12-9.97     -   SrO 0.2-4.15     -   BaO 1.26-4.41     -   ZnO 0-1.0,         wherein the ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of         about 1.0 and 1.6 and the ratio of MgO/(MgO+CaO+SrO+BaO) is in         the range of about 0.22 and 0.37. In various embodiments, the         glass has one or more of: a T(ann)>785° C.; a density <2.65         g/cc; a T(_(200P))<1750° C.; a T(_(35kP))<1340° C.; a Young's         modulus >82 GPa; or an etch index μm/mm³.

One or more embodiments of the disclosure are directed to substantially alkali free glass wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6, the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37. In some embodiments, the glass has one or more of T(ann)>785° C., density <2.65 g/cc, T(200P)<1750° C., T(35 kP)<1340° C., Young's modulus >82 GPa, or an etch index >21 μm/mm³, In various embodiments, the glass comprises, in mol % on an oxide basis, one or more of: SiO₂ in the range 68.14-72.29; Al₂O₃ in the range 11.03-14.18; B₂O₃ in the range 0-2.99; MgO in the range 1.09-7.2; CaO in the range 4.12-9.97; SrO in the range 0.2-4.15; BaO in the range 1.26-4.41; and/or ZnO in the range 0-1.0.

Some embodiments are directed to a substantially alkali free glass wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6, the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37 and the glass has a liquidus viscosity >150 kP. In various embodiments, the glass comprises, in mol % on an oxide basis, one or more of: SiO₂ in the range 68.14-72.29; Al₂O₃ in the range 11.03-14.18; B₂O₃ in the range 0-2.99; MgO in the range 1.09-7.2; CaO in the range 4.12-9.97; SrO in the range 0.2-4.15; BaO in the range 1.26-4.41; and/or ZnO in the range 0-1.0.

One or more embodiments are directed to substantially alkali free glass wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and about 1.6, and the glass has an etch index greater than or equal to 23 μm/mm³, a T(ann)>800° C. and Young's modulus >82 GPa. In various embodiments, the glass comprises, in mol % on an oxide basis, one or more of: SiO₂ in the range 68.14-72.29; Al₂O₃ in the range 11.03-14.18; B₂O₃ in the range 0-2.99; MgO in the range 1.09-7.2; CaO in the range 4.12-9.97; SrO in the range 0.2-4.15; BaO in the range 1.26-4.41; and/or ZnO in the range 0-1.0.

Some embodiments of the disclosure are directed to aluminosilicate glass articles that are substantially free of alkalis, wherein the glass article has an annealing temperature greater than or equal to about 795° C.; a density less than or equal to about 2.63 g/cc; a T_(200P) less than or equal to about 1730° C.; a T_(35kP) less than or equal to about 1320° C.; a Young's modulus greater than or equal to about 81.5 GPa; and an etch index greater than or equal to about 23 μm/mm³. In various embodiments, the aluminosilicate glass article comprises one or more of: SiO₂ in the range of 68.5-72 mol %; greater than or equal to 13 mol % Al₂O₃; B₂O₃ in the range of 0-2.5 mol %; MgO in the range of 1-6 mol %; CaO in the range of 4-8 mol %; SrO in the range 0-4.5 mol %; BaO in the range 0-4.5 mol %; and/or a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ in the range of 1-1.6.

Some embodiments of the disclosure are directed to an aluminosilicate glass article that is substantially free of alkalis, wherein the glass article has an annealing temperature greater than or equal to about 800° C.; a density less than or equal to about 2.61 g/cc; a T_(200P) less than or equal to about 1710° C.; a T_(35kP) less than or equal to about 1310° C.; a Young's modulus greater than or equal to about 81.2 GPa; and an etch index greater than or equal to about 23 μm/mm³. In various embodiments, the aluminosilicate glass article comprises one or more of: SiO₂ in the range of 68.5-72 mol %; greater than or equal to 13 mol % Al₂O₃; B₂O₃ in the range of 0-2.5 mol %; MgO in the range of 1-6 mol %; CaO in the range of 4-8 mol %; SrO in the range 0-4.5 mol %; BaO in the range 0-4.5 mol %; and/or a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ in the range of 1-1.6.

It will be appreciated that the various disclosed embodiments may involve particular features, elements or steps that are described in connection with that particular embodiment. It will also be appreciated that a particular feature, element or step, although described in relation to one particular embodiment, may be interchanged or combined with alternate embodiments in various non-illustrated combinations or permutations.

It is also to be understood that, as used herein the terms “the,” “a,” or “an,” mean “at least one,” and should not be limited to “only one” unless explicitly indicated to the contrary.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

The terms “substantial,” “substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. Moreover, “substantially similar” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially similar” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred.

While various features, elements or steps of particular embodiments may be disclosed using the transitional phrase “comprising,” it is to be understood that alternative embodiments, including those that may be described using the transitional phrases “consisting” or “consisting essentially of,” are implied. Thus, for example, implied alternative embodiments to an apparatus that comprises A+B+C include embodiments where an apparatus consists of A+B+C and embodiments where an apparatus consists essentially of A+B+C.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope of the disclosure. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the disclosure may occur to persons skilled in the art, the disclosure should be construed to include everything within the scope of the appended claims and their equivalents.

Examples

The following examples are set forth below to illustrate the methods and results according to the disclosed subject matter. These examples are not intended to be inclusive of all embodiments of the subject matter disclosed herein, but rather to illustrate representative methods and results. These examples are not intended to exclude equivalents and variations of the present disclosure which are apparent to one skilled in the art.

Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, temperature is in ° C. or is at ambient temperature, and pressure is at or near atmospheric. The compositions themselves are given in mole percent on an oxide basis and have been normalized to 100%. There are numerous variations and combinations of reaction conditions, e.g., component concentrations, temperatures, pressures and other reaction ranges and conditions that can be used to optimize the product purity and yield obtained from the described process. Only reasonable and routine experimentation will be required to optimize such process conditions.

The glass properties set forth in Table 1 were determined in accordance with techniques conventional in the glass art. Thus, the linear coefficient of thermal expansion (CTE) over the temperature range 25-300° C. is expressed in terms of ×10⁻⁷/° C. and the annealing point is expressed in terms of ° C. These were determined from fiber elongation techniques (ASTM references E228-85 and C336, respectively). The density in terms of grams/cm³ was measured via the Archimedes method (ASTM C693). The melting temperature in terms of ° C. (defined as the temperature at which the glass melt demonstrates a viscosity of 200 poises) was calculated employing a Fulcher equation fit to high temperature viscosity data measured via rotating cylinders viscometry (ASTM C965-81).

The liquidus temperature of the glass in terms of ° C. was measured using the standard gradient boat liquidus method of ASTM C829-81. This involves placing crushed glass particles in a platinum boat, placing the boat in a furnace having a region of gradient temperatures, heating the boat in an appropriate temperature region for 24 hours, and determining by means of microscopic examination the highest temperature at which crystals appear in the interior of the glass. More particularly, the glass sample is removed from the Pt boat in one piece, and examined using polarized light microscopy to identify the location and nature of crystals which have formed against the Pt and air interfaces, and in the interior of the sample. Because the gradient of the furnace is very well known, temperature vs. location can be well estimated, within 5-10° C. The temperature at which crystals are observed in the internal portion of the sample is taken to represent the liquidus of the glass (for the corresponding test period). Testing is sometimes carried out at longer times (e.g. 72 hours), to observe slower growing phases. The liquidus viscosity in poises was determined from the liquidus temperature and the coefficients of the Fulcher equation.

Young's modulus values in terms of GPa were determined using a resonant ultrasonic spectroscopy technique of the general type set forth in ASTM E1875-00e1.

Exemplary glasses are shown in Table 1. As can be seen in Table 1, the exemplary glasses have density, annealing point and Young's modulus values that make the glasses suitable for display applications, such as AMLCD substrate applications, and more particularly for low-temperature polysilicon and oxide thin film transistor applications. Although not shown in Table 1, the glasses have durabilities in acid and base media that are similar to those obtained from commercial AMLCD substrates, and thus are appropriate for AMLCD applications. The exemplary glasses can be formed using downdraw techniques, and in particular are compatible with the fusion process, via the aforementioned criteria.

The exemplary glasses of Table 1 were prepared using a commercial sand as a silica source, milled such that 90% by weight passed through a standard U.S. 100 mesh sieve. Alumina was the alumina source, periclase was the source for MgO, limestone the source for CaO, strontium carbonate, strontium nitrate or a mix thereof was the source for SrO, barium carbonate was the source for BaO, and tin (IV) oxide was the source for SnO₂. The raw materials were thoroughly mixed, loaded into a platinum vessel suspended in a furnace heated by silicon carbide glowbars, melted and stirred for several hours at temperatures between 1600 and 1650° C. to ensure homogeneity, and delivered through an orifice at the base of the platinum vessel. The resulting patties of glass were annealed at or near the annealing point, and then subjected to various experimental methods to determine physical, viscous and liquidus attributes.

These methods are not unique, and the glasses of Table 1 can be prepared using standard methods well-known to those skilled in the art. Such methods include a continuous melting process, such as would be performed in a continuous melting process, wherein the melter used in the continuous melting process is heated by gas, by electric power, or combinations thereof.

Raw materials appropriate for producing exemplary glasses include commercially available sands as sources for SiO₂; alumina, aluminum hydroxide, hydrated forms of alumina, and various aluminosilicates, nitrates and halides as sources for Al₂O₃; boric acid, anhydrous boric acid and boric oxide as sources for B₂O₃; periclase, dolomite (also a source of CaO), magnesia, magnesium carbonate, magnesium hydroxide, and various forms of magnesium silicates, aluminosilicates, nitrates and halides as sources for MgO; limestone, aragonite, dolomite (also a source of MgO), wollastonite, and various forms of calcium silicates, aluminosilicates, nitrates and halides as sources for CaO; and oxides, carbonates, nitrates and halides of strontium and barium. If a chemical fining agent is desired, tin can be added as SnO₂, as a mixed oxide with another major glass component (e.g., CaSnO₃), or in oxidizing conditions as SnO, tin oxalate, tin halide, or other compounds of tin known to those skilled in the art.

The glasses in Table 1 contain SnO₂ as a fining agent; but other chemical fining agents could also be employed to obtain glass of sufficient quality for TFT substrate applications. For example, exemplary glasses could employ any one or combinations of As₂O₃, Sb₂O₃, CeO₂, Fe₂O₃, and halides as deliberate additions to facilitate fining, and any of these could be used in conjunction with the SnO₂ chemical fining agent shown in the examples. Of these, As₂O₃ and Sb₂O₃ are generally recognized as hazardous materials, subject to control in waste streams such as might be generated in the course of glass manufacture or in the processing of TFT panels. It is therefore desirable to limit the concentration of As₂O₃ and Sb₂O₃ individually or in combination to no more than 0.005 mol %.

In addition to the elements deliberately incorporated into exemplary glasses, nearly all stable elements in the periodic table are present in glasses at some level, either through low levels of contamination in the raw materials, through high-temperature erosion of refractories and precious metals in the manufacturing process, or through deliberate introduction at low levels to fine tune the attributes of the final glass. For example, zirconium may be introduced as a contaminant via interaction with zirconium-rich refractories. As a further example, platinum and rhodium may be introduced via interactions with precious metals. As a further example, iron may be introduced as a tramp in raw materials, or deliberately added to enhance control of gaseous inclusions. As a further example, manganese may be introduced to control color or to enhance control of gaseous inclusions. As a further example, alkalis may be present as a tramp component at levels up to about 0.1 mol % for the combined concentration of Li₂O, Na₂O and K₂O.

Hydrogen is inevitably present in the form of the hydroxyl anion, OH⁻, and its presence can be ascertained via standard infrared spectroscopy techniques. Dissolved hydroxyl ions significantly and nonlinearly impact the annealing point of exemplary glasses, and thus to obtain the desired annealing point it may be necessary to adjust the concentrations of major oxide components so as to compensate. Hydroxyl ion concentration can be controlled to some extent through choice of raw materials or choice of melting system. For example, boric acid is a major source of hydroxyls, and replacing boric acid with boric oxide can be a useful means to control hydroxyl concentration in the final glass. The same reasoning applies to other potential raw materials comprising hydroxyl ions, hydrates, or compounds comprising physisorbed or chemisorbed water molecules. If burners are used in the melting process, then hydroxyl ions can also be introduced through the combustion products from combustion of natural gas and related hydrocarbons, and thus it may be desirable to shift the energy used in melting from burners to electrodes to compensate. Alternatively, one might instead employ an iterative process of adjusting major oxide components so as to compensate for the deleterious impact of dissolved hydroxyl ions.

Sulfur is often present in natural gas, and likewise is a tramp component in many carbonate, nitrate, halide, and oxide raw materials. In the form of SO₂, sulfur can be a troublesome source of gaseous inclusions. The tendency to form SO₂-rich defects can be managed to a significant degree by controlling sulfur levels in the raw materials, and by incorporating low levels of comparatively reduced multivalent cations into the glass matrix. While not wishing to be bound by theory, it appears that SO₂-rich gaseous inclusions arise primarily through reduction of sulfate (SO₄ ⁼) dissolved in the glass. The elevated barium concentrations of exemplary glasses appear to increase sulfur retention in the glass in early stages of melting, but as noted above, barium is required to obtain low liquidus temperature, and hence high T_(35k)−T_(liq) and high liquidus viscosity. Deliberately controlling sulfur levels in raw materials to a low level is a useful means of reducing dissolved sulfur (presumably as sulfate) in the glass. In particular, sulfur is preferably less than 200 ppm by weight in the batch materials, and more preferably less than 100 ppm by weight in the batch materials.

Reduced multivalents can also be used to control the tendency of exemplary glasses to form SO₂ blisters. While not wishing to be bound to theory, these elements behave as potential electron donors that suppress the electromotive force for sulfate reduction. Sulfate reduction can be written in terms of a half reaction such as

SO₄ ⁼→SO₂+O₂+2e ⁻

where e⁻ denotes an electron. The “equilibrium constant” for the half reaction is

K_(eq)=[SO₂][O₂ ][e ⁻]²/[SO₄ ⁼]

where the brackets denote chemical activities, Ideally one would like to force the reaction so as to create sulfate from SO₂, O₂ and 2e⁻. Adding nitrates, peroxides, or other oxygen-rich raw materials may help, but also may work against sulfate reduction in the early stages of melting, which may counteract the benefits of adding them in the first place. SO₂ has very low solubility in most glasses, and so is impractical to add to the glass melting process. Electrons may be “added” through reduced multivalents. For example, an appropriate electron-donating half reaction for ferrous iron (Fe²⁺) is expressed as

2Fe²⁺→2Fe³⁺+2e ⁻

This “activity” of electrons can force the sulfate reduction reaction to the left, stabilizing SO₄ ⁼ in the glass. Suitable reduced multivalents include, but are not limited to, Fe²⁺, Mn²⁺, Sn²⁺, Sb³⁺, As³⁺, V³⁺, Ti³⁺, and others familiar to those skilled in the art. In each case, it may be important to minimize the concentrations of such components so as to avoid deleterious impact on color of the glass, or in the case of As and Sb, to avoid adding such components at a high enough level so as to complication of waste management in an end-user's process.

In addition to the major oxides components of exemplary glasses, and the minor or tramp constituents noted above, halides may be present at various levels, either as contaminants introduced through the choice of raw materials, or as deliberate components used to eliminate gaseous inclusions in the glass. As a fining agent, halides may be incorporated at a level of about 0.4 mol % or less, though it is generally desirable to use lower amounts if possible to avoid corrosion of off-gas handling equipment. In some embodiments, the concentrations of individual halide elements are below about 200 ppm by weight for each individual halide, or below about 800 ppm by weight for the sum of all halide elements.

In addition to these major oxide components, minor and tramp components, multivalents and halide fining agents, it may be useful to incorporate low concentrations of other colorless oxide components to achieve desired physical, optical or viscoelastic properties. Such oxides include, but are not limited to, TiO₂, ZrO₂, HfO₂, Nb₂O₅, Ta₂O₅, MoO₃, WO₃, ZnO, In₂O₃, Ga₂O₃, BiO₃, GeO₂, PbO, SeO₃, TeO₂, Y₂O₃, La₂O₃, Gd₂O₃, and others known to those skilled in the art. Through an iterative process of adjusting the relative proportions of the major oxide components of exemplary glasses, such colorless oxides can be added to a level of up to about 2 mol % without unacceptable impact to annealing point, T_(35k)−T_(liq) or liquidus viscosity.

Table 1 shows examples of glasses (samples 1-189) with a T(ann)>795° C., a Young's modulus >81.5; and etch index >23, a density <2.63, a T(_(200P))<1730° C.; and a T(_(35kP))<1320° C., Table 2 shows additional examples (samples 190-426) of glasses that border the parameters of Table 1.

TABLE 1 Sample 1 2 3 4 5 6 7 8 SiO₂ 69.99 70.3 70.45 70.84 70.32 70.7 70.56 70.57 Al₂O₃ 13.57 13.43 13.1 13.11 13.35 13.35 13.31 13.29 B₂O₃ 1.84 1.76 1.91 1.97 1.77 1.85 1.85 1.84 MgO 4.47 4.05 3.73 3.32 4.15 3.71 3.94 3.9 CaO 5.1 5.25 5.19 5.13 5.28 4.92 4.86 4.84 SrO 1.04 1.23 1.18 1.19 1.22 1.2 1.2 1.22 BaO 3.89 3.87 3.86 3.86 3.8 4.16 4.14 4.22 ZnO 0 0 0.49 0.49 0 0 0 0 SnO₂ 0.09 0.08 0.07 0.07 0.08 0.1 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.01 0.01 0.02 0.01 0.02 0.02 RO/Al₂O₃ 1.07 1.07 1.07 1.03 1.08 1.05 1.06 1.07 Annealing point 803.1 804.1 797.1 799.5 803.4 805.0 803.1 803.6 Young's modulus 83.2 82.9 82.6 82.0 82.9 82.3 82.3 81.9 Etch index 25.3 25.1 24.1 23.3 24.9 24.5 24.6 24.8 Density 2.598 2.605 2.61 2.606 2.603 2.601 2.609 2.61 T(200 P) 1673 1681 1676 1687 1680 1695 1683 1686 T(35 kP) 1296 1300 1299 1304 1299 1307 1306 1307 T(liquidus) 1220 1200 1205 1230 1200 1200 1220 1210 Liquidus Viscosity 172156 299437 259980 160017 293477 344633 215090 276815 Sample 9 10 11 12 13 14 15 16 SiO₂ 70.38 70.49 69.72 70.59 70.8 70.83 70.83 70.82 Al₂O₃ 13.35 13.18 13.77 13.02 13 13.17 13.2 13.2 B₂O₃ 1.72 1.67 1.56 1.63 1.65 1.7 1.75 1.79 MgO 4.15 4.23 2.87 4.36 4.05 3.81 3.73 3.69 CaO 5.27 5.25 6.51 5.22 5 4.93 4.9 4.89 SrO 1.23 1.22 2.27 1.22 1.23 1.22 1.22 1.22 BaO 3.81 3.84 3.2 3.85 4.15 4.23 4.26 4.27 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.09 0.07 0.09 0.1 0.1 0.1 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.02 0.02 0.01 0.01 RO/Al₂O₃ 1.08 1.10 1.08 1.13 1.11 1.08 1.07 1.07 Annealing point 801.0 803.4 807.7 802.5 803.1 804.6 804.1 807.0 Young's modulus 82.9 82.9 83.3 82.9 82.4 82.3 82.2 82.1 Etch index 24.9 24.5 28.4 24.3 24.3 24.4 24.5 24.4 Density 2.596 2.605 2.613 2.605 2.612 2.603 2.61 2.603 T(200 P) 1681 1683 1673 1683 1693 1697 1690 1698 T(35 kP) 1300 1300 1294 1300 1305 1308 1311 1308 T(liquidus) 1210 1210 1245 1200 1220 1200 1205 1195 Liquidus Viscosity 234831 236958 95668 298562 206203 347978 335511 396996 Sample 17 18 19 20 21 22 23 24 SiO₂ 70.75 70.79 70.81 70.8 70.73 70.62 70.51 70.55 Al₂O₃ 13.25 13.28 13.25 13.21 13.16 13.14 13.13 13.1 B₂O₃ 1.78 1.76 1.75 1.73 1.71 1.69 1.68 1.67 MgO 3.68 3.64 3.69 3.76 3.9 4.03 4.14 4.16 CaO 4.89 4.88 4.9 4.98 5.08 5.19 5.29 5.3 SrO 1.22 1.22 1.22 1.22 1.23 1.23 1.24 1.24 BaO 4.3 4.3 4.26 4.19 4.08 3.99 3.9 3.87 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.1 0.1 0.09 0.09 0.09 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.02 0.02 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.06 1.06 1.06 1.07 1.09 1.10 1.11 1.11 Annealing point 804.4 805.1 804.9 804.6 803.9 806.0 802.7 802.8 Young's modulus 82.2 82.2 82.2 82.3 82.4 82.6 82.8 82.8 Etch index 24.7 24.6 24.5 24.5 24.5 24.6 24.7 24.6 Density 2.614 2.613 2.612 2.61 2.609 2.598 2.606 2.597 T(200 P) 1697 1699 1698 1696 1692 1688 1684 1684 T(35 kP) 1308 1309 1309 1307 1305 1303 1300 1301 T(liquidus) 1190 1215 1210 1210 1205 1220 1205 1215 Liquidus Viscosity 446666 250286 279227 272947 293653 196863 266563 211488 Sample 25 26 27 28 29 30 31 32 SiO₂ 70.65 70.66 70.61 70.62 70.73 70.42 70.29 70.25 Al₂O₃ 13.09 13.07 13.12 13.12 13.05 13.3 13.38 13.38 B₂O₃ 1.67 1.66 1.65 1.69 1.62 1.89 2.01 2.06 MgO 4.12 4.12 4.14 4.12 4.14 4.14 4.1 4.1 CaO 5.3 5.3 5.31 5.3 5.3 5.03 5 5 SrO 1.24 1.24 1.24 1.24 1.23 1.12 1.12 1.11 BaO 3.84 3.85 3.82 3.81 3.83 3.99 3.99 3.99 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.11 1.11 1.11 1.10 1.11 1.07 1.06 1.06 Annealing point 803.1 804.0 803.5 803.2 803.6 802.3 801.4 800.8 Young's modulus 82.7 82.7 82.8 82.7 82.8 82.6 82.5 82.5 Etch index 24.3 24.3 24.4 24.3 24.1 24.5 24.7 24.8 Density 2.603 2.597 2.603 2.602 2.603 2.603 2.603 2.602 T(200 P) 1686 1686 1685 1685 1687 1684 1682 1682 T(35 kP) 1302 1302 1301 1301 1302 1301 1300 1299 T(liquidus) 1230 1225 1200 1215 1205 1215 1215 1220 Liquidus Viscosity 153437 172226 307133 215283 278162 213109 208030 182951 Sample 33 34 35 36 37 38 39 40 SiO₂ 70.26 70.22 70.28 70.57 70.36 70.34 70.54 70.77 Al₂O₃ 13.39 13.41 13.41 13.16 13.3 13.34 13.14 13.02 B₂O₃ 2.01 2.05 2 2.06 2.13 2.1 1.93 1.69 MgO 4.12 4.09 4.09 3.82 3.86 3.88 3.84 3.86 CaO 5 5.01 5 4.87 5.14 5.18 5.18 5.17 SrO 1.12 1.12 1.12 1.54 1.25 1.2 1.41 1.53 BaO 3.99 4 4 3.9 3.88 3.88 3.87 3.88 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.06 0.06 0.06 0.06 0.06 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.02 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.06 1.06 1.06 1.07 1.06 1.06 1.09 1.11 Annealing point 801.4 801.0 804.0 801.4 802.6 803.0 804.0 805.0 Young's modulus 82.5 82.5 82.5 82.1 82.4 82.3 82.3 82.4 Etch index 24.8 24.9 24.8 24.5 24.7 24.7 24.7 24.6 Density 2.603 2.603 2.596 2.603 2.6 2.597 2.604 2.606 T(200 P) 1682 1681 1682 1690 1689 1683 1687 1691 T(35 kP) 1299 1299 1300 1309 1302 1300 1301 1304 T(liquidus) 1230 1225 1225 1210 1230 1240 1225 1235 Liquidus Viscosity 146787 162568 165694 284226 154129 117760 170012 143202 Sample 41 42 43 44 45 46 47 48 SiO₂ 70.59 70.72 70.53 70.7 70.49 70.49 70.41 70.66 Al₂O₃ 13.36 13.33 13.3 13.38 13.26 13.31 13.32 13.21 B₂O₃ 1.75 1.75 1.78 1.64 1.91 1.81 1.79 1.55 MgO 3.88 3.87 3.85 3.86 3.92 4.02 4.13 4.1 CaO 5.2 5.18 5.17 5.2 5.2 5.17 5.19 6.7 SrO 1.23 1.2 1.44 1.24 1.52 1.5 1.35 0.95 BaO 3.89 3.86 3.85 3.88 3.61 3.61 3.72 2.73 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 RO/Al₂O₃ 1.06 1.06 1.08 1.06 1.07 1.07 1.08 1.10 Annealing point 805.8 806.2 804.8 807.9 804.1 804.7 804.1 805.1 Young's modulus 82.3 82.6 82.5 82.3 82.6 82.8 82.8 83.6 Etch index 24.5 24.2 24.9 24.4 24.5 24.5 24.7 23.0 Density 2.602 2.6 2.606 2.602 2.6 2.6 2.599 2.57 T(200 P) 1686 1689 1678 1687 1669 1676 1679 1669 T(35 kP) 1305 1306 1302 1307 1293 1301 1300 1298 T(liquidus) 1220 1215 1215 1220 1235 1230 1230 1190 Liquidus Viscosity 210823 238881 223829 218427 116321 153167 151713 383483 Sample 49 50 51 52 53 54 55 56 SiO₂ 71.12 69.59 70.33 69.56 69.31 69.84 69.51 69.57 Al₂O₃ 13.39 13.83 13.43 13.85 13.97 13.85 13.83 13.99 B₂O₃ 0.75 1.9 1.75 2.04 1.72 1.74 2 1.91 MgO 3.56 2.76 4 2.72 2.72 2.68 2.55 2.51 CaO 7.45 6.26 5.21 6.18 7.45 6.26 7.4 6.75 SrO 1.13 1.38 1.23 1.35 0.62 1.56 0.7 1.31 BaO 2.48 4.19 3.93 4.19 4.1 3.96 3.92 3.86 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.09 0.07 0.07 0.07 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.09 1.05 1.07 1.04 1.07 1.04 1.05 1.03 Annealing point 818.3 803.2 804.4 807.1 809.2 807.3 808.2 809.0 Young's modulus 84.4 82.4 82.8 82.9 83.6 82.3 82.7 82.3 Etch index 23.3 28.8 25.1 28.7 29.3 28.3 28.4 28.7 Density 2.575 2.626 2.607 2.614 2.62 2.624 2.611 2.616 T(200 P) 1677 1673 1683 1678 1670 1673 1677 1682 T(35 kP) 1309 1295 1301 1301 1298 1303 1300 1301 T(liquidus) >1270 1200 >1290 >1270 1250 1265 1260 Liquidus Viscosity 305275 105407 70674 80473 Sample 57 58 59 60 61 62 63 64 SiO₂ 70.62 70.66 69.29 69.75 69.61 69.21 69.76 69.75 Al₂O₃ 13.32 13.3 13.98 13.82 13.96 14.06 13.75 13.84 B₂O₃ 1.82 1.79 1.77 1.56 1.58 1.69 1.85 1.83 MgO 3.84 3.82 3.78 2.58 2.41 2.64 2.16 2.1 CaO 5.17 5.16 5.48 6.36 7.27 6.38 7.11 6.41 SrO 1.52 1.62 2.01 2.35 1.61 3.06 2.5 3.25 BaO 3.62 3.56 3.61 3.48 3.45 2.86 2.77 2.73 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.06 0.06 0.07 0.07 0.07 0.07 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.06 1.06 1.06 1.07 1.06 1.06 1.06 1.05 Annealing point 804.1 804.0 804.4 810.7 809.6 808.7 808.9 808.8 Young's modulus 82.7 82.6 83.0 82.9 83.0 83.2 82.5 82.5 Etch index 24.3 24.3 28.5 29.0 28.9 30.0 28.3 28.9 Density 2.599 2.6 2.621 2.623 2.615 2.622 2.603 2.614 T(200 P) 1680 1679 1671 1670 1672 1672 1667 1679 T(35 kP) 1302 1302 1293 1301 1298 1293 1295 1301 T(liquidus) 1215 1235 1240 1280 1270 1235 1230 >1295 Liquidus Viscosity 222583 140296 104063 52848 62035 114644 136873 Sample 65 66 67 68 69 70 71 72 SiO₂ 70.72 70.72 69.11 69.51 69.91 70.02 70.41 69.89 Al₂O₃ 13.05 13.05 14.18 14.03 13.37 13.46 13.29 13.96 B₂O₃ 1.66 1.65 1.77 1.69 1.62 1.7 1.3 1.32 MgO 4.12 4.12 2.14 2.16 3.21 2.91 3.45 2.81 CaO 5.29 5.29 6.86 5.94 6.58 6.62 6.31 6.01 SrO 1.23 1.23 3.14 4.15 2.13 2.2 2.02 2.85 BaO 3.83 3.82 2.71 2.42 3.07 2.99 3.12 3.07 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.07 0.07 0.07 0.06 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.03 0.01 0.01 0.02 0.01 0.01 0.01 RO/Al₂O₃ 1.11 1.11 1.05 1.05 1.12 1.09 1.12 1.06 Annealing point 803.3 806.0 810.5 812.1 801.1 806.0 807.0 812.8 Young's modulus 82.7 82.7 82.7 83.2 82.7 82.6 83.8 83.3 Etch index 24.1 24.1 30.7 30.0 27.3 27.1 26.1 28.6 Density 2.602 2.596 2.617 2.621 2.603 2.602 2.606 2.623 T(200 P) 1687 1687 1667 1677 1666 1680 1671 1687 T(35 kP) 1302 1303 1292 1299 1289 1295 1298 1302 T(liquidus) 1220 1220 1270 1280 1250 1260 1260 1250 Liquidus Viscosity 195363 196370 54101 51305 76993 71088 75283 101098 Sample 73 74 75 76 77 78 79 80 SiO₂ 70.81 69.63 70.49 70.38 70.49 70.81 70.91 70.23 Al₂O₃ 13.32 13.79 13.11 13.2 13.14 13.29 13.31 13.5 B₂O₃ 1.83 1.6 1.05 1.67 1.5 1.84 1.79 1.95 MgO 3.57 3.11 4.12 3.31 3.86 3.62 3.54 3.16 CaO 4.88 5.95 5.99 6.16 5.77 4.87 4.86 6.27 SrO 1.23 2.82 1.81 1.92 1.65 1.23 1.23 0.93 BaO 4.23 3 3.33 3.25 3.48 4.21 4.22 3.87 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.07 0.08 0.08 0.08 0.1 0.1 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.01 0.01 0.01 0.02 0.02 0.01 RO/Al₂O₃ 1.04 1.08 1.16 1.11 1.12 1.05 1.04 1.05 Annealing point 805.2 808.0 808.1 805.5 804.9 804.8 806.0 804.4 Young's modulus 82.1 82.7 83.1 82.5 83.5 82.1 82.1 82.0 Etch index 24.4 28.5 25.7 25.8 25.2 24.3 24.2 25.9 Density 2.61 2.618 2.607 2.603 2.602 2.609 2.609 2.6 T(200 P) 1699 1676 1685 1677 1675 1699 1702 1679 T(35 kP) 1309 1295 1299 1298 1295 1309 1311 1301 T(liquidus) 1200 1230 1250 1260 1230 1195 1200 1240 Liquidus Viscosity 360371 134268 94961 74322 136577 403112 372425 123729 Sample 81 82 83 84 85 86 87 88 SiO₂ 70.1 70.55 70.68 70.84 70.85 70.86 69.97 69.88 Al₂O₃ 13.57 13.26 13.18 13.59 13.44 13.44 13.35 13.35 B₂O₃ 2.01 1.65 1.64 1.43 1.56 1.59 1.63 1.74 MgO 3.06 3.61 3.69 2.3 3.07 3.25 5.1 5.21 CaO 6.4 5.92 5.83 6.43 6.17 6.09 5.05 4.96 SrO 0.83 1.28 1.36 2.19 0.78 0.45 1.29 1.24 BaO 3.94 3.62 3.53 3.12 4.02 4.23 3.5 3.51 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0 0.01 0.01 RO/Al₂O₃ 1.05 1.09 1.09 1.03 1.04 1.04 1.12 1.12 Annealing point 805.3 806.1 801.7 817.2 811.6 810.1 801.6 801.0 Young's modulus 82.3 83.0 82.7 82.7 82.5 82.0 83.1 83.8 Etch index 26.2 24.9 24.5 25.9 24.8 24.6 24.8 24.7 Density 2.6 2.598 2.597 2.597 2.599 2.599 2.601 2.6 T(200 P) 1680 1682 1681 1690 1694 1696 1660 1662 T(35 kP) 1298 1302 1303 1314 1313 1313 1291 1290 T(liquidus) 1230 1230 1230 1270 1250 1230 1220 1220 Liquidus Viscosity 143556 154047 158336 84630 125632 197745 156077 152568 Sample 89 90 91 92 93 94 95 96 SiO₂ 69.84 69.89 69.87 69.83 69.87 69.91 70.1 69.91 Al₂O₃ 13.34 13.28 13.35 13.37 13.3 13.29 13.33 13.4 B₂O₃ 1.7 1.58 1.61 1.75 1.75 1.7 1.48 1.72 MgO 5.23 5.24 5.29 5.28 5.14 5.14 5.13 5.15 CaO 5.05 5.16 5.11 4.98 5.14 5.15 5.01 4.96 SrO 1.09 1.08 0.92 0.94 0.92 0.95 1.12 0.97 BaO 3.64 3.66 3.73 3.73 3.76 3.74 3.72 3.79 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.09 0.08 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.13 1.14 1.13 1.12 1.12 1.13 1.12 1.11 Annealing point 802.0 800.8 800.8 800.9 806.8 801.5 801.9 803.8 Young's modulus 83.9 83.6 83.8 84.3 83.7 83.2 83.4 83.4 Etch index 24.9 25.0 24.8 24.7 24.8 24.8 24.7 24.8 Density 2.602 2.604 2.603 2.602 2.602 2.604 2.601 2.602 T(200 P) 1669 1669 1661 1660 1669 1666 1678 1663 T(35 kP) 1291 1291 1290 1289 1292 1292 1294 1291 T(liquidus) 1235 1220 1230 1225 1215 1225 1230 1230 Liquidus Viscosity 111101 151913 123612 132943 177388 140726 129027 125920 Sample 97 98 99 100 101 102 103 104 SiO₂ 69.77 69.72 69.71 69.83 69.79 69.81 69.83 69.95 Al₂O₃ 13.4 13.29 13.35 13.33 13.34 13.3 13.28 13.38 B₂O₃ 1.61 1.54 1.63 1.68 1.59 1.67 1.59 1.55 MgO 5.56 5.49 5.51 5.37 5.6 5.32 5.29 5.27 CaO 4.95 5.15 5.04 5.01 4.95 5.12 5.22 5.07 SrO 1.03 1.12 0.97 1.06 1.03 1.06 1 1.08 BaO 3.58 3.57 3.68 3.61 3.58 3.61 3.68 3.59 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.09 0.09 0.09 0.08 0.08 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.13 1.15 1.14 1.13 1.14 1.14 1.14 1.12 Annealing point 801.4 801.0 799.0 813.0 800.2 800.0 800.3 801.7 Young's modulus 83.8 84.3 84.3 83.8 84.0 82.9 83.7 84.5 Etch index 24.8 25.2 25.0 24.8 24.7 24.9 25.1 24.7 Density 2.602 2.605 2.604 2.603 2.603 2.603 2.603 2.603 T(200 P) 1658 1656 1661 1665 1655 1670 1665 1672 T(35 kP) 1285 1286 1287 1289 1286 1291 1293 1291 T(liquidus) 1235 1235 1240 1220 1235 1230 1235 1230 Liquidus Viscosity 99725 101205 91240 154337 100790 124064 117558 122727 Sample 105 106 107 108 109 110 111 112 SiO₂ 69.98 69.96 70.2 70.35 70.41 70.2 70.42 70.11 Al₂O₃ 13.38 13.41 13.37 13.32 13.3 13.24 13.17 13.39 B₂O₃ 1.64 1.72 1.67 1.62 1.55 1.67 1.71 1.8 MgO 5.1 4.97 4.93 4.35 4.38 4.64 4.47 4.55 CaO 5.01 4.97 4.93 5.43 5.47 5.38 5.33 5.07 SrO 1.32 1.41 1.41 1.25 1.11 1.11 0.92 1.06 BaO 3.46 3.41 3.37 3.58 3.67 3.66 3.86 3.91 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.13 0.08 0.07 0.08 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.11 1.10 1.09 1.10 1.10 1.12 1.11 1.09 Annealing point 800.9 801.4 801.7 805.3 804.9 801.1 801.1 801.4 Young's modulus 83.6 83.2 83.6 82.9 84.8 83.2 82.7 82.9 Etch index 24.7 24.6 24.1 24.6 24.5 24.7 24.2 25.0 Density 2.599 2.597 2.596 2.601 2.598 2.599 2.6 2.604 T(200 P) 1666 1667 1686 1673 1678 1680 1678 1667 T(35 kP) 1292 1296 1295 1298 1297 1299 1302 1299 T(liquidus) 1240 1235 1235 1220 1210 1210 1210 1205 Liquidus Viscosity 102206 125777 117377 178550 218096 232664 227454 266595 Sample 113 114 115 116 117 118 119 120 SiO₂ 70.08 70.05 70.03 70.21 70.62 69.05 68.95 69.24 Al₂O₃ 13.42 13.43 13.4 13.46 13.19 13.9 13.98 14.01 B₂O₃ 1.74 1.65 1.65 1.78 1.55 1.74 1.8 1.75 MgO 4.06 4.06 4.1 4.15 3.62 5.64 5.68 4.99 CaO 5.73 5.86 5.84 5.31 5.8 4.8 4.74 5.21 SrO 1.33 1.42 1.45 1.23 1.61 1.27 1.33 1.09 BaO 3.52 3.43 3.44 3.77 3.49 3.48 3.4 3.59 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.07 0.07 0.08 0.08 0.1 0.1 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.01 0.01 0.02 0.01 0.01 0.02 RO/Al₂O₃ 1.09 1.10 1.11 1.07 1.10 1.09 1.08 1.06 Annealing point 800.6 802.6 801.8 801.6 807.8 801.7 801.1 804.0 Young's modulus 83.5 83.1 83.2 83.0 82.7 84.4 84.7 83.7 Etch index 25.5 25.7 25.8 25.2 24.9 26.4 26.4 26.5 Density 2.601 2.6 2.602 2.602 2.602 2.605 2.605 2.605 T(200 P) 1669 1666 1671 1675 1687 1646 1666 1665 T(35 kP) 1292 1290 1293 1299 1311 1281 1281 1285 T(liquidus) 1200 1210 1210 1200 1210 1260 1265 1250 Liquidus Viscosity 253804 192535 205963 295023 301915 53250 48335 70816 Sample 121 122 123 124 125 126 127 128 SiO₂ 70.26 70.39 69.85 69.91 69.99 69.41 69.61 69.58 Al₂O₃ 13.44 13.36 13.56 13.83 13.75 13.93 13.85 13.67 B₂O₃ 1.76 1.77 1.88 1.5 1.54 1.77 1.77 1.94 MgO 4.1 4.11 5.49 4.75 5.05 5.65 4.91 5.61 CaO 5.29 5.26 4.12 5.09 4.59 4.5 5.12 4.26 SrO 1.23 1.22 1.22 1.37 1.62 0.86 1.31 1.17 BaO 3.83 3.79 3.78 3.44 3.35 3.76 3.33 3.66 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.09 0.08 0.08 0.09 0.09 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.08 1.08 1.08 1.06 1.06 1.06 1.06 1.08 Annealing point 803.0 803.8 800.4 807.2 806.3 801.5 802.4 799.1 Young's modulus 82.9 82.9 83.8 83.5 84.1 84.1 84.0 83.6 Etch index 25.2 24.7 24.4 25.3 24.8 25.2 25.4 24.7 Density 2.597 2.602 2.606 2.602 2.599 2.603 2.597 2.602 T(200 P) 1679 1681 1659 1673 1670 1662 1667 1651 T(35 kP) 1299 1300 1287 1294 1293 1285 1290 1286 T(liquidus) 1200 1200 1255 1250 1260 1270 1250 1250 Liquidus Viscosity 293138 299747 66447 85885 67578 47292 78823 73461 Sample 129 130 131 132 133 134 135 136 SiO₂ 70.92 71.09 70.66 70.63 70.02 70 70.95 70.87 Al₂O₃ 13.28 13.19 13.17 13.18 13.31 13.39 13.08 13.17 B₂O₃ 1.74 1.79 1.96 1.97 1.66 1.67 1.6 1.79 MgO 3.71 3.72 3.77 3.77 4.92 4.89 3.57 3.76 CaO 5.2 4.88 5.2 5.25 4.91 5.2 5.34 5.01 SrO 1.18 1.4 1.23 1.2 1.22 1.19 1.67 1.46 BaO 3.87 3.83 3.9 3.9 3.84 3.56 3.71 3.86 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.07 0.07 0.07 0.07 0.08 0.08 0.07 0.06 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.05 1.05 1.07 1.07 1.12 1.11 1.09 1.07 Annealing point 804.3 805.8 804.5 803.8 802.0 801.4 806.0 803.2 Young's modulus 82.5 82.0 82.1 82.0 83.6 83.4 83.6 82.1 Etch index 23.7 23.3 24.2 24.3 25.1 24.9 24.4 24.1 Density 2.597 2.6 2.598 2.599 2.607 2.597 2.605 2.602 T(200 P) 1688 1687 1685 1683 1669 1668 1693 1689 T(35 kP) 1309 1310 1306 1306 1294 1293 1311 1309 T(liquidus) 1200 1200 1205 1200 1230 1230 1250 1230 Liquidus Viscosity 366072 367712 299762 340083 133668 131035 119851 180252 Sample 137 138 139 140 141 142 143 144 SiO₂ 71 70.14 70.29 70.67 70.46 71.06 71 70.42 Al₂O₃ 13.13 13.35 13.2 13 13.09 13.09 13.08 13.19 B₂O₃ 1.81 1.63 1.63 1.56 1.62 1.46 1.63 1.74 MgO 3.79 4.7 4.47 4.41 5.16 3.89 3.63 4.44 CaO 4.9 5.36 5.37 5.48 4.94 5.64 5.76 5.24 SrO 1.42 1.2 1.26 1.08 1.04 1.19 1.22 1.09 BaO 3.87 3.53 3.67 3.7 3.58 3.58 3.57 3.78 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.06 0.08 0.08 0.08 0.08 0.07 0.07 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.06 1.11 1.12 1.13 1.12 1.09 1.08 1.10 Annealing point 804.1 801.7 804.8 800.3 801.1 806.8 808.0 804.2 Young's modulus 82.4 83.7 83.5 83.4 83.6 83.0 82.0 83.1 Etch index 23.6 24.8 24.8 23.9 23.3 23.4 23.6 24.3 Density 2.601 2.598 2.603 2.597 2.593 2.593 2.592 2.601 T(200 P) 1688 1676 1672 1681 1673 1673 1688 1673 T(35 kP) 1307 1293 1298 1300 1303 1300 1305 1296 T(liquidus) 1220 1200 1215 1200 1225 1220 1220 1210 Liquidus Viscosity 218578 256994 203181 298265 180021 191362 208334 222007 Sample 145 146 147 148 149 150 151 152 SiO₂ 70.16 70.06 70.05 70.08 70.45 70.14 70.24 70.67 Al₂O₃ 13.36 13.48 13.44 13.43 13.3 13.38 13.29 13.07 B₂O₃ 1.77 1.73 1.74 1.76 1.66 1.68 1.68 1.57 MgO 4.46 4.43 4.36 4.22 4.23 4.4 4.32 4.25 CaO 5.22 5.3 5.37 5.53 5.52 5.53 5.57 5.36 SrO 1.1 1.21 1.18 1.22 1.22 1.23 1.19 1.32 BaO 3.82 3.68 3.74 3.65 3.52 3.54 3.61 3.66 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.08 0.07 0.07 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.02 0.02 0.02 0.01 RO/Al₂O₃ 1.09 1.08 1.09 1.09 1.09 1.10 1.11 1.12 Annealing point 804.0 803.7 802.9 804.6 805.2 804.1 804.3 806.3 Young's modulus 83.1 82.7 83.8 82.3 83.2 83.6 83.6 82.9 Etch index 24.9 25.2 25.3 25.3 24.3 25.0 24.9 24.1 Density 2.604 2.604 2.603 2.601 2.598 2.597 2.599 2.601 T(200 P) 1675 1672 1672 1670 1673 1673 1679 1678 T(35 kP) 1303 1299 1297 1298 1299 1297 1304 1302 T(liquidus) 1210 1210 1210 1215 1220 1225 1210 1215 Liquidus Viscosity 250642 234066 226948 201805 185345 159888 262331 219739 Sample 153 154 155 156 157 158 159 160 SiO₂ 70.67 70.63 70.4 70.43 70.38 70.24 70.6 70.64 Al₂O₃ 13.3 13.24 13.31 13.46 13.09 13.16 13.16 13.4 B₂O₃ 1.91 1.75 1.75 1.85 1.95 1.94 1.69 1.65 MgO 3.8 3.8 4.12 3.76 3.75 3.76 4.11 3.83 CaO 4.92 5.15 4.88 5.29 5.19 5.22 5.29 5.28 SrO 1.17 1.35 1.22 1.2 1.18 1.2 1.21 1.22 BaO 4.09 3.97 4.21 3.91 3.88 3.9 3.83 3.88 ZnO 0 0 0 0 0.49 0.49 0 0 SnO₂ 0.09 0.09 0.09 0.07 0.07 0.07 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.05 1.08 1.08 1.05 1.07 1.07 1.10 1.06 Annealing point 804.8 806.1 804.5 804.7 796.1 797.0 804.6 805.6 Young's modulus 82.0 82.5 82.6 82.0 82.3 82.8 82.5 82.3 Etch index 24.2 24.7 25.2 24.9 24.2 24.6 24.3 24.6 Density 2.606 2.608 2.613 2.599 2.609 2.611 2.597 2.599 T(200 P) 1683 1681 1682 1671 1679 1675 1684 1680 T(35 kP) 1313 1307 1305 1302 1299 1299 1307 1304 T(liquidus) 1220 1200 1220 1210 1215 1215 1215 1210 Liquidus Viscosity 255607 349191 209625 249804 204351 204311 244630 258866 Sample 161 162 163 164 165 166 167 168 SiO₂ 70.64 70.6 70.58 70.3 70.52 70.78 69.81 70.39 Al₂O₃ 13.29 13.17 13.11 13.42 13.29 13.17 13.56 13.43 B₂O₃ 1.72 1.68 1.68 1.91 1.87 1.76 1.81 1.84 MgO 4.12 3.9 4.06 4.07 3.88 3.72 2.67 4.09 CaO 5.2 5.63 5.26 5.06 4.85 4.92 6.86 5 SrO 1.19 1.03 1.24 1.17 1.23 1.36 2.34 1.11 BaO 3.74 3.88 3.96 3.96 4.24 4.18 2.86 4.02 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.07 0.08 0.08 0.08 0.09 0.09 0.07 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.02 0.02 0.02 0.01 0.01 0.02 RO/Al₂O₃ 1.07 1.10 1.11 1.06 1.07 1.08 1.09 1.06 Annealing point 806.9 804.5 805.3 803.6 803.9 805.0 804.7 803.9 Young's modulus 81.5 82.3 82.6 82.3 82.3 82.5 83.2 82.7 Etch index 24.0 24.5 24.7 24.9 24.9 24.6 27.8 24.7 Density 2.595 2.6 2.603 2.606 2.609 2.612 2.604 2.605 T(200 P) 1686 1689 1674 1686 1686 1694 1677 1685 T(35 kP) 1308 1305 1303 1301 1308 1309 1295 1302 T(liquidus) 1230 1220 1230 1225 1220 1210 1270 1200 Liquidus Viscosity 175734 205013 160621 167882 223645 285128 57440 311772 Sample 169 170 171 172 173 174 175 176 SiO₂ 70.71 69.41 70.67 70.76 69.86 70.38 69.99 70.26 Al₂O₃ 13.35 13.67 13.2 13.19 13.61 13.36 13.52 13.45 B₂O₃ 1.84 1.79 1.8 1.83 1.88 1.74 1.83 1.82 MgO 3.64 2.79 3.68 3.83 4.17 4.13 4.2 4.18 CaO 4.89 7.01 4.89 4.65 5.29 5.27 5.3 5.21 SrO 1.22 2.43 1.39 1.39 1.22 1.22 1.21 1.19 BaO 4.22 2.81 4.25 4.24 3.86 3.8 3.84 3.78 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.06 0.09 0.09 0.08 0.08 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.05 1.10 1.08 1.07 1.07 1.08 1.08 1.07 Annealing point 807.1 802.6 805.2 804.4 804.2 804.0 802.8 802.8 Young's modulus 81.7 82.8 81.8 81.8 83.2 82.9 82.9 82.7 Etch index 24.6 28.8 25.0 24.5 26.0 24.8 25.7 24.8 Density 2.609 2.606 2.611 2.612 2.619 2.603 2.603 2.601 T(200 P) 1680 1660 1697 1694 1656 1681 1671 1674 T(35 kP) 1307 1288 1310 1309 1292 1300 1299 1299 T(liquidus) 1200 1280 1230 1215 >1290 1190 1260 1225 Liquidus Viscosity 351625 40932 182596 251502 381805 76623 165703 Sample 177 178 179 180 181 182 183 184 SiO₂ 70.19 70.19 70.19 70.21 70.22 70.75 70.88 70.74 Al₂O₃ 13.46 13.46 13.46 13.45 13.44 13.37 13.31 13.3 B₂O₃ 1.78 1.78 1.79 1.93 1.99 1.8 1.78 1.78 MgO 3.66 3.41 3.15 4.16 4.14 3.56 3.56 3.7 CaO 5.31 5.32 5.31 5.06 5.04 4.88 4.89 4.98 SrO 1.23 1.23 1.23 1.13 1.11 1.24 1.24 1.23 BaO 3.77 3.77 3.77 3.96 3.95 4.26 4.22 4.14 ZnO 0.5 0.75 1 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.08 0.08 0.1 0.1 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.02 RO/Al₂O₃ 1.04 1.02 1.00 1.06 1.06 1.04 1.05 1.06 Annealing point 801.6 800.3 797.9 802.0 803.5 805.6 807.0 805.0 Young's modulus 83.5 83.2 82.8 82.5 82.9 82.2 82.2 82.3 Etch index 24.8 24.7 24.5 25.0 24.9 24.6 24.3 24.5 Density 2.609 2.611 2.616 2.603 2.603 2.612 2.602 2.609 T(200 P) 1682 1678 1670 1678 1679 1699 1700 1696 T(35 kP) 1299 1298 1290 1304 1303 1309 1310 1308 T(liquidus) 1240 1240 1200 1200 1195 Liquidus Viscosity 132042 128110 360038 366709 392214 Sample 185 186 187 188 189 SiO₂ 69.78 70.37 69.65 69.57 71.06 Al₂O₃ 13.36 13.11 13.91 13.94 13.07 B₂O₃ 1.71 1.98 1.73 1.81 1.47 MgO 5.44 3.72 2.87 2.43 3.65 CaO 4.91 5.2 5.7 6.35 5.22 SrO 1.06 1.18 2.75 2.63 1.16 BaO 3.63 3.86 3.29 3.16 3.8 ZnO 0 0.49 0 0 0.48 SnO₂ 0.09 0.07 0.07 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.13 1.06 1.05 1.05 1.06 Annealing point 798.9 799.1 808.6 808.3 803.4 Young's modulus 83.6 82.3 82.8 82.9 82.9 Etch index 24.8 24.2 28.7 29.1 23.0 Density 2.603 2.61 2.623 2.617 2.613 T(200 P) 1674 1672 1672 1676 1686 T(35 kP) 1289 1296 1300 1296 1304 T(liquidus) 1230 1205 1240 1245 1220 Liquidus Viscosity 116376 238010 121655 99336 204831

TABLE 2 Sample 190 191 192 193 194 195 196 197 SiO₂ 71.84 71.24 70.7 72.05 72.04 71.86 70.83 71.14 Al₂O₃ 12.18 12.39 12.69 12.61 12.73 12.09 13.08 13.32 B₂O₃ 1.05 2.12 2.12 1.42 1.39 1.05 1.59 0.95 MgO 4.39 4.06 3.88 3.84 3.65 4.42 4.09 3.63 CaO 5.26 5.17 5.13 5.33 5.28 5.26 6.57 7.23 SrO 1.17 1.24 1.29 1.75 1.59 1.16 0.93 1.08 BaO 3.99 3.63 3.99 2.9 3.21 4.03 2.81 2.53 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.12 0.11 0.08 0.08 0.1 0.07 0.08 Fe₂O₃ 0.01 0.01 0.08 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.02 0.02 0.01 0.01 0.01 0.02 0.02 RO/Al₂O₃ 1.215928 1.138015 1.126084 1.095956 1.078555 1.229942 1.100917 1.086336 Annealing 805.4355 795 793 809.1221 811.7 804.6045 803.3 818 point Young's 82.63852 81.3 82.2 82.62262 82.3 82.56992 82.3 84.28304 modulus Etch index 21.98403 21.80912 23.78082 20.40033 20.84532 21.94227 22.56788 22.8704 Density 2.587 2.604 2.581 2.57 2.573 T(200 P) 1706 1681 1674 1710 1705 1707 1629 1635 T(35 kP) 1312 1305 1305 1316 1321 1312 1280 1284 T(liqui- 1200 1175 1180 1220 1220 1200 1180 >1260 dus) Liquidus 376241.5 606709 529676.2 254710.6 295398.1 373256.9 500709.9 Viscosity Sample 198 199 200 201 202 203 204 205 SiO₂ 71.58 71.31 71.33 71.62 71.63 71.56 71.29 71.2 Al₂O₃ 12.34 12.62 11.49 11.3 11.45 11.7 12.52 11.96 B₂O₃ 1.2 2.65 1.29 0 0 1.27 2.42 1.82 MgO 4.34 3.54 5.21 5.42 5.98 4.86 3.91 4.52 CaO 5.26 5.13 5.33 5.79 5.42 5.26 5 5.71 SrO 1.18 1.17 1.28 1.54 1.4 1.4 1.2 1.76 BaO 3.96 3.47 3.91 4.14 3.93 3.8 3.51 2.88 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.11 0.14 0.14 0.13 0.12 0.11 Fe₂O₃ 0.01 0.01 0.02 0.02 0.02 0.02 0.01 0.02 ZrO₂ 0.02 0.02 0.02 0.02 0.02 0 0.02 0.02 RO/Al₂O₃ 1.194489 1.054675 1.369017 1.49469 1.461135 1.309402 1.087859 1.243311 Annealing 807 796.8 793.2 803.5 804.7 791.5 793.3 794.2 point Young's 82.6139 80.2 82.8 83.2 83.4 82.6 81.3 83.2 modulus Etch index 22.40229 21.08061 22.37395 23.8956 22.798 22.00998 21.09513 21.65186 Density 2.6 2.568 2.612 2.641 2.633 2.614 2.578 2.58 T(200 P) 1702 1688 1680 1688 1689 1685 1683 1677 T(35 kP) 1310 1312 1295 1303 1303 1295 1308 1300 T(liqui- 1210 1190 1190 1200 1200 1190 1180 1200 dus) Liquidus 283765.7 490718.9 331896.6 318618.2 322560.5 323644.3 576117.8 290070.4 Viscosity Sample 206 207 208 209 210 211 212 213 SiO₂ 71.59 71.5 71.49 71.05 71.69 72.1 71.38 71.8 Al₂O₃ 11.74 11.94 12.3 11.79 11.76 11.58 12.24 12.42 B₂O₃ 1.99 1.35 1.67 0.83 0.81 0.79 1.75 1.64 MgO 4.17 4.49 4.03 4.93 4.73 4.64 4.18 4.01 CaO 5.29 5.34 5.3 5.74 5.53 5.46 5.33 5.16 SrO 2.56 1.48 1.26 1.43 1.39 1.37 1.26 1.22 BaO 2.53 3.76 3.81 4.07 3.92 3.88 3.72 3.6 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.11 0.11 0.11 0.13 0.13 0.13 0.11 0.11 Fe₂O₃ 0.01 0.02 0.02 0.02 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.02 0.02 0.02 0.01 0.01 RO/Al₂O₃ 1.239353 1.262144 1.170732 1.371501 1.32398 1.325561 1.183824 1.126409 Annealing 793.1 799.8 798.3 796 800.1 801.1 794.4 798.4 point Young's 81.8 82.2 81.9 83.1 83 81.8 82.2 82.09687 modulus Etch index 20.94944 22.40757 22.14761 24.45907 22.58831 21.49573 22.09737 20.93307 Density 2.574 2.603 2.597 2.632 2.62 2.613 2.595 2.591 T(200 P) 1686 1693 1689 1679 1696 1703 1685 1695 T(35 kP) 1298 1304 1303 1295 1309 1312 1298 1304 T(liqui- 1200 1190 1185 1180 1190 1195 1190 1190 dus) Liquidus 273184.9 404439.6 450027.9 431437.8 447459.2 417832.3 348549.8 404582.5 Viscosity Sample 214 215 216 217 218 219 220 221 SiO₂ 71.23 71.46 71.12 70.76 70.72 71.01 71.26 71.37 Al₂O₃ 12.41 12.59 11.2 12.25 12.14 12.36 11.86 11.84 B₂O₃ 2.54 2.58 0.69 3 2.13 1.85 1.81 1.84 MgO 3.62 3.54 5.84 3.69 4.86 4.13 4.57 4.36 CaO 5.23 5.1 5.52 5.69 5.81 5.32 6.13 6.29 SrO 1.42 1.18 1.04 2.58 1.91 1.3 1.42 1.22 BaO 3.43 3.43 4.41 1.91 2.32 3.87 2.84 2.97 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.09 0.11 0.09 0.08 0.12 0.09 0.08 Fe₂O₃ 0.01 0.01 0.05 0.02 0.02 0.03 0.01 0.01 ZrO₂ 0.01 0.02 0.02 0.02 0.01 0.02 0.02 0.02 RO/Al₂O₃ 1.103948 1.052423 1.500893 1.132245 1.227348 1.182848 1.261383 1.253378 Annealing 798.2 796.1127 792.8 785.5 786 794.4 793.4782 791.4 point Young's 81 81.05578 83.1 81.1 82.65483 82 82.434 81.8 modulus Etch index 21.62558 20.69529 23.76489 21.38514 21.68129 23.17525 21.31421 21.19108 Density 2.57 2.633 2.551 2.559 2.602 2.572 T(200 P) 1687 1705 1672 1677 1681 1686 T(35 kP) 1310 1309 1289 1304 1295 1302 T(liqui- 1195 1185 1185 1180 1180 1205 1210 dus) Liquidus 412527.4 491868.8 328005.3 377073.8 536073.1 230732.6 234784.7 Viscosity Sample 222 223 224 225 226 227 228 229 SiO₂ 70.31 71.14 70.31 70.72 70.93 70.84 70.61 71.43 Al₂O₃ 13.21 11.82 12.42 12.9 12.03 12.19 13.13 12.4 B₂O₃ 2.53 1.63 2.36 2.24 2.2 2.2 2.73 2.16 MgO 3.46 5.06 4.33 3.69 4.6 4.34 3.38 3.89 CaO 4.8 5.87 5.27 4.98 5.19 5.26 4.65 5.26 SrO 1.27 1.7 1.28 1.24 1.15 1.26 1.25 1.77 BaO 4.15 2.66 3.88 4.09 3.76 3.78 4.12 2.97 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.11 0.1 0.11 0.1 0.11 0.11 0.1 0.09 Fe₂O₃ 0.14 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.02 0.02 0.02 0.02 0.02 0.01 RO/Al₂O₃ 1.035579 1.29357 1.188406 1.085271 1.221945 1.200984 1.020564 1.120161 Annealing 788.8 794.1 789.8 797.3 787.1 790.2 792.7 797.5 point Young's 81.5 82.8977 81.1 80.3 81.5 81.7 80.9 81 modulus Etch index 24.4386 21.39602 24.17951 23.88871 22.27046 22.895 23.70371 21.09214 Density 2.607 2.596 2.601 2.589 2.594 2.598 2.573 T(200 P) 1665 1676 1670 1682 1677 1679 1673 1677 T(35 kP) 1305 1292 1294 1305 1295 1295 1303 1306 T(liqui- 1190 1180 1170 1170 1175 1205 1195 dus) Liquidus 426531.6 416885.2 694785.4 525798.2 472442.8 278595.7 387294.1 Viscosity Sample 230 231 232 233 234 235 236 237 SiO₂ 70.21 70.4 70.74 70.92 70.74 71.51 72.23 71.33 Al₂O₃ 13.27 13.25 13 12.31 12.25 12.39 12.76 11.65 B₂O₃ 2.57 2.52 2.48 2.21 2.3 1.96 1.15 1.78 MgO 3.51 3.41 3.35 3.93 4.26 3.88 3.57 4.3 CaO 4.82 4.58 4.58 5.2 4.93 5.2 5.3 5.39 SrO 1.24 1.42 1.43 1.24 1.26 1.21 1.54 1.38 BaO 4.24 4.29 4.28 4.04 4.12 3.72 3.33 4.03 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.1 0.1 0.11 0.11 0.1 0.08 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.02 0.02 0.01 0.01 0.02 RO/Al₂O₃ 1.040693 1.033962 1.049231 1.170593 1.189388 1.130751 1.076803 1.296137 Annealing 794.7 796.5 795.9 792.5 791.7 795.5 813.7858 789.5 point Young's 81.6 81.1 80.7 80.7 81.1 81.3 82.6638 81.7 modulus Etch index 25.05352 24.90785 24.11577 23.27226 23.43973 21.61804 20.8276 22.79115 Density 2.606 2.606 2.605 2.602 2.605 2.585 2.606 T(200 P) 1673 1672 1681 1684 1687 1689 1719 1689 T(35 kP) 1297 1304 1307 1302 1302 1308 1322 1300 T(liqui- 1210 1215 1190 1190 1205 1180 1220 1175 dus) Liquidus 219801 231632 431798.8 377500.1 266069.2 551290.9 290830.5 508628.1 Viscosity Sample 238 239 240 241 242 243 244 245 SiO₂ 71.02 70.54 71.34 71.27 71.32 71.27 72.29 71.13 Al₂O₃ 12.62 13.29 11.63 11.65 11.59 11.52 12.76 11.27 B₂O₃ 2 2.72 1.78 1.8 1.88 1.95 1.1 0.91 MgO 4.24 3.49 4.19 4.29 4.09 4.29 3.59 5.68 CaO 5.11 4.55 5.53 5.46 5.7 5.5 5.3 5.46 SrO 1.17 1.1 1.28 1.21 1.07 0.89 1.53 1.1 BaO 3.69 4.18 4.12 4.18 4.21 4.43 3.32 4.27 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.11 0.1 0.1 0.1 0.1 0.1 0.08 0.11 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.04 ZrO₂ 0.02 0.02 0.02 0.02 0.02 0.02 0.01 0.02 RO/Al₂O₃ 1.12599 1.002257 1.300086 1.299571 1.300259 1.311632 1.076803 1.464951 Annealing 797.3 795.7 788.5 789.1 789.1 787.5 816.3 791.7 point Young's 82.4 80.9 81.2 81.4 81.3 81.3 83.1 82.4 modulus Etch index 22.36433 23.68105 22.9597 22.99637 22.90863 22.8298 20.72019 23.39862 Density 2.59 2.596 2.606 2.607 2.607 2.611 2.587 2.629 T(200 P) 1685 1679 1686 1688 1690 1689 1697 1675 T(35 kP) 1305 1306 1302 1302 1299 1299 1324 1290 T(liqui- 1180 1220 1180 1180 1180 1190 1220 1190 dus) Liquidus 536290.9 212391.7 477341 469814.6 444046.2 343194.4 326959.3 293380 Viscosity Sample 246 247 248 249 250 251 252 253 SiO₂ 70.99 71.54 71.22 71.48 71.19 71.48 71.59 71.49 Al₂O₃ 11.8 12.52 11.67 11.36 11.59 11.58 11.55 11.57 B₂O₃ 1.2 2.29 1.7 1.45 1.55 1.52 1.53 1.61 MgO 5.57 3.64 4.85 4.87 5.02 4.53 4.33 4.4 CaO 5.36 5.07 5.31 5.35 5.44 5.43 5.52 5.45 SrO 1.84 1.19 1.15 0.98 1.21 1.37 1.29 1.22 BaO 3.08 3.64 3.97 4.38 3.86 3.96 4.04 4.12 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.11 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Fe₂O₃ 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.03 0.01 0.02 0.02 0.02 0.02 0.02 0.02 RO/Al₂O₃ 1.34322 1.08147 1.30934 1.371479 1.339948 1.32038 1.314286 1.312878 Annealing 795.7 797.5 790.9 789.7 791.6 792.7 793.2 794.7 point Young's 83.1 81.3 81.9 82 83 82.2 81.8 80.9 modulus Etch index 22.44066 21.13801 22.40309 22.51773 22.47967 22.49214 22.3657 22.50857 Density 2.6 2.578 2.602 2.617 2.605 2.608 2.609 2.61 T(200 P) 1675 1698 1686 1686 1680 1688 1694 1699 T(35 kP) 1292 1311 1298 1300 1295 1304 1302 1304 T(liqui- 1195 1175 1175 1200 1190 1185 1180 1180 dus) Liquidus 277980.5 668710.1 494723.9 285342.4 324060.7 440344.3 474815.8 494159.7 Viscosity Sample 254 255 256 257 258 259 260 261 SiO₂ 71.51 71.48 72.45 72.99 72.36 72.04 72.47 72.95 Al₂O₃ 11.58 11.77 12.55 12.52 12.92 12.67 12.35 12.14 B₂O₃ 1.62 1.55 1.39 0.88 0.74 1.01 1.15 1.17 MgO 4.23 4.46 3.51 3.58 3.7 4.02 4.08 4 CaO 5.65 5.52 5.21 5.12 5.22 5.11 4.97 4.87 SrO 1.08 1.14 1.51 1.29 1.24 1.24 1.2 1.18 BaO 4.2 3.96 3.26 3.51 3.7 3.79 3.66 3.57 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.09 0.09 0.08 0.08 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.01 0.02 0.02 0.02 0.02 0.02 RO/Al₂O₃ 1.309154 1.281223 1.0749 1.078275 1.072755 1.117601 1.126316 1.121911 Annealing 794.6 795.5 813.2 822 821.3 813 811.7 811.3 point Young's 81.6 81.9 82.2 83.1 83.6 83.3 83 82.3 modulus Etch index 22.64522 22.29207 19.83529 19.16165 21.09868 21.45792 19.84445 18.45087 Density 2.61 2.608 2.579 2.584 2.598 2.597 2.59 2.581 T(200 P) 1695 1682 1699 1729 1713 1705 1712 1720 T(35 kP) 1303 1300 1321 1337 1334 1326 1324 1332 T(liqui- 1175 1170 1200 1230 1210 1210 1205 1230 dus) Liquidus 548444.6 608512.8 479431.2 323282.9 507430.5 412573.2 434357.2 291555.9 Viscosity Sample 262 263 264 265 266 267 268 269 SiO₂ 72.36 72.2 72.13 71.8 71.87 71.45 71.51 71.36 Al₂O₃ 12.34 12.49 12.44 12.38 12.07 12.49 12.24 12.58 B₂O₃ 1.01 0.95 0.85 1.58 1.05 2.51 1.62 2.45 MgO 4.37 4.5 4.71 4.28 4.46 3.54 4.65 3.86 CaO 5.36 5.58 5.67 5.52 5.25 5.28 5.66 4.94 SrO 2.62 3.16 3.2 2.73 1.16 1.16 2.59 1.19 BaO 1.82 1.01 0.88 1.59 4.03 3.45 1.61 3.47 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.1 0.09 0.09 0.12 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.01 0.01 0.02 0.02 0.01 0.02 RO/Al₂O₃ 1.148298 1.140913 1.162379 1.140549 1.234466 1.07526 1.185458 1.069952 Annealing 812.6031 810.9 813.4 802.6 804.3335 797.4 798.6 796.4516 point Young's 83.50687 84.8 84.6 82.3 82.57827 81.8 83.6 81.33516 modulus Etch index 19.03153 18.89465 18.90793 19.65592 21.93579 20.90369 20.02251 20.80924 Density 2.548 2.547 2.553 2.571 2.556 0 T(200 P) 1706 1691 1691 1685 1706 1689 1676 1702 T(35 kP) 1314 1313 1310 1307 1312 1309 1301 1308 T(liqui- 1240 1260 1265 1240 1205 1190 1250 1195 dus) Liquidus 159186.9 101972.6 85719.78 137559.8 328769.2 453473.6 97743.74 377911.9 Viscosity Sample 270 271 272 273 274 275 276 277 SiO₂ 71.39 72.63 72.86 71.58 71.85 69.92 70.66 71.97 Al₂O₃ 12.45 12.35 11.08 12.39 12.63 12.46 12.29 12.33 B₂O₃ 2.28 1.04 0.28 2.39 1.69 1.66 1.81 1.24 MgO 3.93 4.48 7.28 3.52 3.91 5.78 4.87 4.32 CaO 5.18 4.78 3.91 5.35 5.05 6.42 6.04 5.23 SrO 1.59 1.06 0.45 1.16 1.2 1.64 1.52 1.2 BaO 3.06 3.54 4.04 3.48 3.53 2.02 2.67 3.59 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.11 0.09 0.09 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.02 0.01 0.02 0.01 0 0.02 0.01 RO/Al₂O₃ 1.105221 1.122267 1.415162 1.090395 1.083927 1.272873 1.228641 1.163017 Annealing 798.8 812.3432 809.4 798.7 806 794.4814 795.0042 805.9 point Young's 82.2 82.8007 83.8 80.8 82.13926 84.34114 83.05592 82.7 modulus Etch index 20.90878 18.84683 17.00156 20.79405 20.6446 23.1501 22.34058 20.84849 Density 2.571 2.596 2.573 2.584 2.589 T(200 P) 1680 1723 1708 1690 1701 1642 1668 1704 T(35 kP) 1306 1324 1321 1310 1314 1275 1289 1318 T(liqui- 1200 1250 1275 1200 1185 1255 1190 dus) Liquidus 340722.7 152460.4 87073.22 368579.7 583021.9 52829.21 554503 Viscosity Sample 278 279 280 281 282 283 284 285 SiO₂ 70.86 71.83 71.44 72.51 71.39 71.28 71.23 72.71 Al₂O₃ 11.75 12.08 12.41 12.49 12.61 12.57 12.56 11.22 B₂O₃ 1.31 1.05 1.29 1.04 2.41 2.59 2.69 0.23 MgO 5.53 4.44 4.35 4.27 3.85 3.07 3.83 6.66 CaO 5.4 5.26 5.2 4.92 4.93 5.7 4.9 3.65 SrO 1.77 1.16 1.15 1.18 1.18 1.17 1.18 2.49 BaO 3.22 4.04 4.03 3.47 3.49 3.49 3.47 2.93 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.11 0.1 0.09 0.09 0.11 0.1 0.11 0.09 Fe₂O₃ 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.01 RO/Al₂O₃ 1.354894 1.233444 1.186946 1.108086 1.066614 1.068417 1.065287 1.401961 Annealing 793.1 804.3726 803.5725 813.2185 800.4 795.7 795.7 812 point Young's 83.3 82.57328 82.55808 82.84625 81.4 80.9 80.8 84.2 modulus Etch index 22.82465 21.9954 22.71064 19.3897 20.82856 21.8111 20.86149 18.3739 Density 2.601 2.601 2.574 2.574 2.57 2.598 T(200 P) 1673 1706 1700 1721 1685 1688 1682 1707 T(35 kP) 1289 1312 1309 1323 1310 1312 1305 1320 T(liqui- 1190 1215 1195 1220 1195 1180 1180 1255 dus) Liquidus 294185.9 260080.1 394781.1 297066.7 423662.6 618602.3 528537.5 128091.6 Viscosity Sample 286 287 288 289 290 291 292 293 SiO₂ 72.62 72.29 72.32 71.73 71.25 69.76 71.33 71.27 Al₂O₃ 12.37 11.9 11.74 12.36 12.59 13.31 12.54 12.54 B₂O₃ 1.04 0.38 0.16 1.63 2.64 2.08 2.2 2.17 MgO 4.52 4.99 5.08 3.66 3.3 4.53 3.76 3.86 CaO 4.74 5.24 5.37 5.64 5.42 6.43 5.31 5.3 SrO 1.04 1.15 1.18 1.18 1.17 1.02 1.61 1.73 BaO 3.54 3.91 4.03 3.68 3.48 2.75 3.13 3.03 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.1 0.1 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.02 0.02 0.02 0.01 0.01 RO/Al₂O₃ 1.118836 1.284874 1.333901 1.145631 1.061954 1.106687 1.101276 1.110048 Annealing 813.8 811.2404 814.7 799 795 794.9 798 796.5 point Young's 82.83213 83.46431 83.60945 81.94595 75.9 83.4 81.70809 81.8 modulus Etch index 18.77549 21.04342 21.51927 21.75296 21.46548 24.26216 21.47102 21.61943 Density 2.578 2.619 2.591 2.572 2.573 2.574 2.575 T(200 P) 1715 1710 1707 1689 1653 1698 1691 T(35 kP) 1326 1316 1324 1309 1284 1306 1307 T(liqui- 1240 1220 1225 1175 1190 1210 1185 dus) Liquidus 204010 254527.6 278235.6 640934.2 275491.3 255656.1 475116 Viscosity Sample 294 295 296 297 298 299 300 301 SiO₂ 71.33 71.68 71.8 72.36 72.04 71.45 71.3 71.32 Al₂O₃ 12.54 12.07 11.91 11.65 12.2 12.36 12.41 12.45 B₂O₃ 2.05 1.39 1.13 1.06 2.41 2.6 2.63 2.53 MgO 3.97 4.39 4.56 4.66 3.17 3.52 3.59 3.68 CaO 5.37 5.39 5.42 5.4 5.2 5.05 5.05 5.12 SrO 1.77 1.36 1.21 1.11 2.55 1.96 1.82 1.45 BaO 2.86 3.6 3.84 3.63 2.31 2.93 3.09 3.34 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.09 0.09 0.1 0.1 0.1 0.1 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.02 0.02 0.01 0.02 0.01 0.01 0.01 RO/Al₂O₃ 1.114035 1.22121 1.261965 1.270386 1.084426 1.088997 1.091861 1.091566 Annealing 798.4 800.843 801.3 800.3 798 797.5 795.8 795.8 point Young's 82.2 82.39273 81.9 82.7 83.5 80.9 80.6 81.3 modulus Etch index 21.32183 21.6436 21.73829 19.88012 19.59274 20.79872 21.23157 21.23147 Density 2.572 2.592 2.603 2.609 2.554 2.562 2.565 2.57 T(200 P) 1679 1700 1688 1694 1697 1691 1676 1678 T(35 kP) 1304 1307 1308 1313 1318 1314 1308 1307 T(liqui- 1190 1200 1195 1190 1190 1200 1180 1190 dus) Liquidus 415004.2 337331.2 402056.3 489179.1 543289.1 400055 575999 442857.5 Viscosity Sample 302 303 304 305 306 307 308 309 SiO₂ 71.2 71.31 71.15 71.29 71.54 72.09 70.45 71.17 Al₂O₃ 12.44 12.59 12.58 12.4 11.03 10.81 13.17 12.55 B₂O₃ 2.54 2.37 2.62 2.63 0 0 2.47 1.92 MgO 3.71 3.7 3.52 3.54 5.47 5.34 3.53 3.94 CaO 5.19 5.24 5.38 5.4 5.94 5.84 4.83 5.17 SrO 1.4 1.42 1.18 1.16 1.55 1.52 1.24 1.24 BaO 3.4 3.26 3.44 3.47 4.29 4.22 4.17 3.89 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.09 0.09 0.09 0.14 0.14 0.1 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.02 0.02 0.01 0.01 ZrO₂ 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.02 RO/Al₂O₃ 1.101286 1.081811 1.074722 1.094355 1.563917 1.565217 1.045558 1.134661 Annealing 797.1 796.6 795.6 794.3 799.8 798.7 795.6 795.4 point Young's 81.4 81.7 81 81.2 83.5 83.4 81.3 81.9 modulus Etch index 21.54734 21.32736 21.57075 21.28039 24.42145 22.92993 24.44992 22.7997 Density 2.572 2.572 2.573 2.57 2.652 2.645 2.602 2.594 T(200 P) 1684 1682 1682 1689 1682 1684 1681 1687 T(35 kP) 1309 1310 1307 1309 1296 1298 1304 1306 T(liqui- 1190 1190 1185 1180 1190 1205 1195 1165 dus) Liquidus 457698.6 471657.5 491185 575435.4 344528.5 248518.1 366301.6 786689.9 Viscosity Sample 310 311 312 313 314 315 316 317 SiO₂ 71.14 70.86 70.99 71.35 71.39 72.51 72.24 71.14 Al₂O₃ 11.82 12.07 12.03 11.78 12.65 12.31 12.51 11.79 B₂O₃ 1.63 1.67 1.61 1.59 2.62 1.37 0.95 1.72 MgO 5.06 5.17 5.14 4.98 3.77 3.54 4.15 4.64 CaO 5.87 5.71 5.7 5.85 4.84 5.28 5.4 6.59 SrO 1.7 2.02 1.99 1.67 1.17 3.19 2.19 1.19 BaO 2.66 2.38 2.42 2.68 3.41 1.7 2.43 2.82 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.1 0.09 0.09 0.12 0.08 0.1 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.02 RO/Al₂O₃ 1.29357 1.265949 1.267664 1.288625 1.042688 1.113729 1.132694 1.292621 Annealing 794.1 795.1323 793.6 793.2 795.8 810.1711 813.7264 792.8048 point Young's 82.8977 83.19961 83.2 83.1 81.5 82.57109 83.37436 82.66717 modulus Etch index 21.39602 21.82925 21.6186 21.00684 20.41822 19.28765 20.01173 21.59617 Density 2.574 2.575 2.57 T(200 P) 1676 1670 1669 1676 1690 1715 1709 1675 T(35 kP) 1292 1290 1293 1297 1307 1318 1316 1291 T(liqui- 1200 1210 1190 1230 dus) Liquidus 251949 214753.2 434855.9 211230.1 Viscosity Sample 318 319 320 321 322 323 324 325 SiO₂ 70.19 71.04 68.14 70.44 71.94 70.69 70.39 70.74 Al₂O₃ 13.07 11.79 12.54 12.15 12.25 12.37 12.49 13.09 B₂O₃ 2.26 1.69 0.92 1.51 1.01 1.83 1.92 1.67 MgO 4.63 4.77 7.2 5.81 4.62 4.91 4.99 5.19 CaO 6.17 6.71 7.07 5.81 5.45 5.81 5.18 4.04 SrO 0.02 1.17 2.71 2.11 1.24 1.62 1.18 1.84 BaO 3.55 2.72 1.31 2.06 3.38 2.65 3.73 3.34 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.08 0.09 0.1 0.09 0.09 0.09 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0 0 0.02 0.02 0.01 0 RO/Al₂O₃ 1.099464 1.303647 1.458533 1.299588 1.199184 1.211803 1.207366 1.10084 Annealing 794.3 788.7 793.0213 795.3731 807.6744 792.1 794.1 805 point Young's 83.5 82.6 86.64271 84.02072 83.1448 83.2 82.4 82.9 modulus Etch index 22.87987 21.66993 28.00262 22.31177 20.84279 22.23753 23.72841 22.68145 Density 2.575 2.57 2.574 2.6 2.593 T(200 P) 1659 1679 1592 1655 1702 1666 1670 1690 T(35 kP) 1290 1290 1248 1282 1311 1290 1290 1304 T(liqui- 1210 1210 >1250 1270 1200 1200 1155 1240 dus) Liquidus 192476.4 181711 44402.08 371517.1 239421.5 702527.8 129265.8 Viscosity Sample 326 327 328 329 330 331 332 333 SiO₂ 70.27 71.82 72.5 71.74 71.2 70.52 72.22 71.86 Al₂O₃ 12.84 12.29 12.21 12.97 11.59 12.43 11.77 12.07 B₂O₃ 2.01 1.02 0.27 0.38 1.19 2.99 0.62 1.05 MgO 4.83 5.14 5.18 5.14 5.32 3.84 6.6 4.44 CaO 5.69 5.28 5.37 5.34 5.36 5.06 3.38 5.26 SrO 1.63 2.03 1.59 1.57 1.4 1.2 2.09 1.17 BaO 2.61 2.31 2.76 2.76 3.78 3.84 3.2 4.03 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.11 0.09 0.09 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.01 ZrO₂ 0.02 0 0 0 0.02 0.02 0.01 0.01 RO/Al₂O₃ 1.149533 1.200976 1.220311 1.141866 1.368421 1.12148 1.297366 1.234466 Annealing 794 808.4483 817.8526 820.4832 795.1 787.8 807.6 807 point Young's 83.6 83.82911 84.36218 84.89179 83.3 80.3 84 82.56772 modulus Etch index 23.01219 19.9231 19.30305 21.10905 22.69538 23.03402 18.96296 21.96634 Density 2.575 2.612 2.585 2.596 2.601 T(200 P) 1651 1691 1706 1693 1680 1674 1697 1706 T(35 kP) 1286 1306 1316 1311 1294 1292 1316 1312 T(liqui- 1190 1310 1270 1260 1200 1165 1260 1200 dus) Liquidus 283259 32303.36 87589.07 98776.53 255014.6 550608.6 108909.5 370555.6 Viscosity Sample 334 335 336 337 338 339 340 341 SiO₂ 70.64 71.56 70.53 69.39 70.88 71.13 71.52 70.89 Al₂O₃ 12.82 12.87 13.58 13.54 12.63 12.47 11.95 12.13 B₂O₃ 2.33 1.17 1.29 2.17 1.93 1.82 1.92 1.05 MgO 4.1 5.06 5.08 4.81 3.55 3.19 3.95 6.04 CaO 6.18 5.18 5.16 6.21 7.06 7.35 6.51 5.14 SrO 0.12 1.97 2 1.11 0.48 0.63 0.88 1.37 BaO 3.68 2.06 2.25 2.64 3.36 3.29 3.17 3.25 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.12 0.09 0.09 0.09 0.09 0.08 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0 0 0.02 0.02 0.02 0.02 0.01 RO/Al₂O₃ 1.098284 1.10878 1.06701 1.090842 1.144101 1.159583 1.214226 1.302556 Annealing 794.6 812.23 812.5898 794.2 798.1 798 792.9 800.6779 point Young's 82.4 84.17108 84.64822 83.6 82.4 82.5 82.2 83.98618 modulus Etch index 22.31073 19.86527 22.6712 24.68895 22.9674 22.90319 21.03888 22.22297 Density 2.574 2.573 2.575 2.577 2.572 T(200 P) 1670 1688 1670 1644 1666 1691 1683 1672 T(35 kP) 1297 1306 1297 1280 1295 1308 1301 1293 T(liqui- 1185 1240 1260 1220 1190 1190 1170 dus) Liquidus 396614.3 136428.3 75061.55 124995.4 348107.7 448058.3 612361.5 Viscosity Sample 342 343 344 345 346 347 348 349 SiO₂ 70.62 70.78 70.84 71.16 71.54 70.51 72.29 71.63 Al₂O₃ 13.09 13.01 12.76 13.66 12.46 12.87 12.28 12.53 B₂O₃ 1.5 1.34 2.05 0.52 2.47 2.25 0.83 1.32 MgO 4.84 4.87 3.85 5.04 3.47 4.28 1.09 3.32 CaO 5.75 5.66 6.46 5.25 5.19 6.09 9.97 7.26 SrO 1.52 1.63 0.86 1.54 1.38 0.44 0.41 1.08 BaO 2.58 2.59 3.08 2.72 3.39 3.44 3.01 2.73 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.07 0.09 0.08 0.09 0.1 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0 0.01 0.02 0.02 0.02 RO/Al₂O₃ 1.122231 1.133743 1.116771 1.065154 1.077849 1.107226 1.179153 1.148444 Annealing 802.9 804.7 795 823.3371 798.2 796.0502 818.8 808.5 point Young's 83.3 84.7 82.3 85.27518 81.04604 82.47254 82 82.7 modulus Etch index 22.63284 22.45787 22.4536 22.28574 20.94774 22.59134 23.17745 21.72726 Density 2.575 2.577 2.571 2.569 2.576 2.567 T(200 P) 1661 1668 1669 1685 1690 1675 1704 1686 T(35 kP) 1296 1300 1298 1308 1310 1294 1324 1312 T(liqui- 1190 1190 1180 1260 1170 1210 >1300 1250 dus) Liquidus 367592.1 396125.9 463848.9 94542.68 757926.6 204023.8 124458.6 Viscosity Sample 350 351 352 353 354 355 356 357 SiO₂ 71.55 72.22 70.97 72.65 72.53 71.56 71.49 71.08 Al₂O₃ 12.65 12.3 12.4 11 11.27 12.45 12.47 12.09 B₂O₃ 1.52 1.7 1.98 0.08 0.19 2.41 2.42 1.1 MgO 4.51 4.46 4.01 7.31 6.94 3.54 3.57 5.96 CaO 5.73 5.4 6.51 3.92 4.22 5.17 5.18 4.98 SrO 1.39 1.37 0.88 1.82 1.49 1.38 1.38 1.51 BaO 2.54 2.44 3.15 3.12 3.24 3.4 3.4 3.17 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.09 0.09 0.08 0.08 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.120158 1.111382 1.173387 1.47 1.409938 1.083534 1.085004 1.291977 Annealing 803.2 802.3 794.6 808.9 809.7 796.296 796.025 797.5 point Young's 83.2 82.6 82.3 84.1 83.8 81.13427 81.16879 83.7 modulus Etch index 20.24181 18.02948 22.27053 17.92624 18.23479 20.95388 21.10237 21.75035 Density 2.563 2.551 2.573 2.596 2.595 2.594 T(200 P) 1680 1697 1676 1699 1702 1706 1704 1672 T(35 kP) 1310 1315 1296 1316 1315 1309 1308 1297 T(liqui- 1230 1235 1195 >1285 1270 1220 dus) Liquidus 187896.9 182059.8 307135.7 84862.08 175526.4 Viscosity Sample 358 359 360 361 362 363 364 365 SiO₂ 71.06 71.54 71.62 72.62 73.01 72.89 73.06 73.16 Al₂O₃ 12.11 11.79 11.64 10.9 10.72 10.94 10.9 10.67 B₂O₃ 1.01 0.93 0.64 0.21 0.23 0.36 0.41 0.23 MgO 5.99 6.02 6.61 7.03 7.07 7.73 7.51 7.38 CaO 5.08 4.5 4.4 4.33 4.41 3.32 3.23 3.74 SrO 1.37 2.57 2.15 1.51 1.41 0.77 1.63 1.56 BaO 3.26 2.54 2.84 3.28 3.04 3.88 3.13 3.14 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.296449 1.3257 1.37457 1.481651 1.486007 1.435101 1.422018 1.482662 Annealing 798.1 799.3 800.8 806.1 806 808 806.8 808.1 point Young's 83.4 83.4 83.8 83.8 83.8 83.6 84.5 84.2 modulus Etch index 21.88896 20.78711 20.49126 18.07284 16.59969 16.33879 15.73304 15.99909 Density 2.594 2.592 2.596 2.596 2.582 2.592 2.583 2.582 T(200 P) 1668 1675 1677 1698 1701 1707 1708 1711 T(35 kP) 1297 1302 1300 1312 1317 1320 1320 1321 T(liqui- 1220 1215 1225 1280 1290 >1300 1300 >1295 dus) Liquidus 176802.1 217348.4 166314.4 65505.18 58957.97 50968.15 Viscosity Sample 366 367 368 369 370 371 372 373 SiO₂ 72.78 71.19 70.36 72.46 72.88 72.95 72.92 73.17 Al₂O₃ 10.93 12.44 12.52 11.5 11.07 11.11 10.9 10.75 B₂O₃ 0.1 1.6 2.91 0.51 0.23 0.07 0.17 0.2 MgO 7.32 4.43 3.95 6.78 6.87 6.84 6.97 7.17 CaO 3.89 5.48 5.11 3.36 4.22 3.74 3.32 3.96 SrO 1.75 1.07 1.2 2.09 0.89 2.37 3.27 1.51 BaO 3.12 3.69 3.83 3.18 3.73 2.81 2.34 3.12 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.08 0.09 0.09 0.09 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.02 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.47118 1.17926 1.125399 1.34 1.419151 1.418542 1.458716 1.466047 Annealing 809.2 800 788.8 807.6 809.4 811.3 808 807.8 point Young's 84.1 80.6 80.7 84.1 84.7 84.1 84.3 84 modulus Etch index 17.44481 22.48081 23.46576 18.33199 17.44799 17.54849 17.53955 16.16689 Density 2.592 2.592 2.584 2.595 2.597 2.591 2.593 2.584 T(200 P) 1703 1684 1676 1703 1705 1708 1714 1710 T(35 kP) 1317 1302 1292 1319 1321 1321 1317 1321 T(liqui- >1270 1195 1170 1255 1280 1280 1280 >1290 dus) Liquidus 345017.6 487482.8 127262.8 77703.34 68543.02 65484.62 Viscosity Sample 374 375 376 377 378 379 380 381 SiO₂ 72.96 72.89 72.79 71.98 72.06 72.05 72.31 72.32 Al₂O₃ 11.12 11.27 11.48 12.16 12.23 12.53 12.25 12.43 B₂O₃ 0.2 0.2 0.25 0.56 0.53 0.62 0.44 0.45 MgO 6.36 6.09 6.23 5.62 5.94 5.12 5.02 5.1 CaO 3.9 3.87 3.91 4.56 4 4.69 4.68 4.66 SrO 2.7 3.1 2.14 1.74 1.76 1.6 2.29 1.51 BaO 2.64 2.46 3.08 3.27 3.37 3.29 2.9 3.41 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.402878 1.377107 1.337979 1.249178 1.232216 1.173184 1.21551 1.181014 Annealing 810.2 811.4 811.7 809.9 811.6 811.6 814.3 817.9 point Young's 84 84 83.8 83.9 84 84.3 84.5 83.8 modulus Etch index 17.86931 18.40311 18.35774 20.59488 20.12042 20.63091 20.43909 20.19099 Density 2.59 2.592 2.594 2.598 2.598 2.597 2.596 2.597 T(200 P) 1712 1715 1711 1697 1702 1706 1700 1704 T(35 kP) 1323 1324 1325 1320 1318 1320 1321 1324 T(liqui- 1280 1250 1260 1220 1230 1220 1220 1220 dus) Liquidus 69511.87 156090.9 127513.5 287263.6 218144.5 257540.4 263908.4 278800.4 Viscosity Sample 382 383 384 385 386 387 388 389 SiO₂ 71.71 71.84 71.18 71.19 71.64 71.84 71.68 71.08 Al₂O₃ 12.09 12.08 12.57 12.59 12.64 12.79 12.84 12.26 B₂O₃ 1.08 0.98 1.18 1.22 0.96 1 0.87 2.12 MgO 4.5 4.51 4.71 4.7 4.07 3.99 4.84 2.18 CaO 5.42 5.29 5.5 5.51 5.53 5.14 4.79 8.35 SrO 1.14 1.16 1.32 1.33 1.31 1.38 1.17 0.51 BaO 3.92 4 3.43 3.33 3.72 3.73 3.68 3.37 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.1 0.09 0.08 0.1 0.1 0.1 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 RO/Al₂O₃ 1.239041 1.238411 1.190135 1.181096 1.157437 1.11337 1.127726 1.175367 Annealing 804.1 805.4 804.6 804.9 810.9 813.8 813.1 795.5 point Young's 82.6 82.6 83.2 83.35358 83.07044 83.1 83.8 81.4 modulus Etch index 22.08195 21.95745 22.68694 22.42529 22.64597 22.05351 21.52961 23.8085 Density 2.605 2.611 2.596 2.594 2.606 2.601 2.601 2.577 T(200 P) 1693 1693 1685 1682 1699 1708 1695 1683 T(35 kP) 1313 1315 1303 1302 1313 1321 1315 1299 T(liqui- 1185 1190 1190 1190 1190 1180 1190 1230 dus) Liquidus 569667.5 536744.4 397758.3 393454.2 511895.1 778849.7 539338.6 142246.1 Viscosity Sample 390 391 392 393 394 395 396 397 SiO₂ 72.33 72.68 71.29 71.24 71.99 72.05 72.26 71.14 Al₂O₃ 12.39 12.46 13.23 13.35 12.8 12.5 12.44 11.82 B₂O₃ 0.87 0.45 1.2 1.12 0.37 0.94 0.99 1.63 MgO 4.38 5.08 5.17 5.33 5.41 4.55 4.47 5.06 CaO 5.63 4.77 3.78 3.47 4.69 5.1 5.6 5.87 SrO 1.09 1.29 1.94 1.94 1.36 1.25 3.04 1.7 BaO 3.21 3.16 3.29 3.47 3.25 3.49 1.1 2.66 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.07 0.07 0.07 0.07 0.07 0.09 0.09 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0 0 0.02 0.02 0.01 0.01 RO/Al₂O₃ 1.154964 1.147673 1.071807 1.064419 1.149219 1.1512 1.142283 1.29357 Annealing 812.7514 820.2 811.1 799.4 819.8 812 813.8677 794.1 point Young's 83.32084 84.1 83.6 83.5 84.7 83 83.99441 82.8977 modulus Etch index 19.84819 18.70819 21.76007 22.05945 20.45227 20.68442 18.75206 21.39602 Density 2.582 2.595 2.601 2.592 2.591 2.552 T(200 P) 1710 1706 1693 1698 1703 1694 1697 1676 T(35 kP) 1317 1328 1311 1312 1316 1318 1311 1292 T(liqui- 1220 1240 1240 1260 1265 1210 1250 dus) Liquidus 263835.1 218400.7 151844.1 100264.2 97254.47 358760.1 Viscosity Sample 398 399 400 401 402 403 404 405 SiO₂ 71.83 72.85 72.18 71.78 70.25 70.54 71.82 72.35 Al₂O₃ 12.12 11.17 12.05 12.38 12.6 12.8 12.24 12.06 B₂O₃ 1.05 0.09 0.6 0.82 2.09 1.71 0.88 0.43 MgO 4.44 6.79 5.41 4.96 4.83 4.83 4.85 5.3 CaO 5.25 3.83 4.78 5.16 5.77 5.72 5.57 4.8 SrO 1.17 2.34 1.69 1.47 1.5 1.6 1.26 1.74 BaO 4.02 2.83 3.16 3.31 2.85 2.7 3.28 3.21 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.09 0.1 0.1 0.08 0.08 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.01 0.01 0.02 0.02 0.02 0.01 RO/Al₂O₃ 1.227723 1.413608 1.248133 1.203554 1.186508 1.160156 1.222222 1.247927 Annealing 804.7055 811.3 810.4 808.5 793.4 798.7 808.8 813.6 point Young's 82.61094 84.5 83.8 83.3 82.5 82.9 83.2 83.5 modulus Etch index 22.0199 17.87469 20.00777 21.23817 23.26557 22.86863 21.09331 20.06004 Density 2.6 2.593 2.593 2.593 2.579 2.579 2.588 2.597 T(200 P) 1706 1709 1701 1695 1662 1667 1696 1700 T(35 kP) 1312 1320 1317 1314 1287 1295 1315 1320 T(liqui- 1190 1240 1210 1210 1180 1180 1215 1205 dus) Liquidus 472860.5 178135 344750.8 314204.8 368621.5 436103.1 292593.6 422856.3 Viscosity Sample 406 407 408 409 410 411 412 413 SiO₂ 72.05 71.92 71.9 72.09 71.93 70.52 72.29 71.75 Al₂O₃ 12.27 12.33 12.37 12.3 12.34 12.97 12.48 12.46 B₂O₃ 0.49 0.65 0.68 0.51 0.66 2.32 1.02 0.88 MgO 5.06 5.01 4.94 4.98 4.97 3.65 4.08 4.82 CaO 5.15 5.15 5.19 5.21 5.19 4.95 5.38 5.23 SrO 1.5 1.48 1.45 1.41 1.44 1.27 2.26 1.41 BaO 3.37 3.34 3.35 3.4 3.35 4.07 2.38 3.32 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.09 0.09 0.08 0.09 0.11 0.09 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.11 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.02 0.01 0.01 RO/Al₂O₃ 1.229014 1.214923 1.206952 1.219512 1.211507 1.074788 1.129808 1.186196 Annealing 811.9 811.05 810 812 810.25 793.9 815.3 808.1 point Young's 84.1 83.4 83.75 84 83.65 82.1 83.4 83.4 modulus Etch index 21.04336 21.11301 21.1736 20.96679 21.09031 24.03389 19.89371 21.28791 Density 2.598 2.595 2.5955 2.598 2.5955 2.605 2.593 T(200 P) 1699 1698 1698 1699 1697 1678 1704 1697 T(35 kP) 1318 1317 1316 1320 1317 1304 1322 1313 T(liqui- 1200 1207.5 1205 1200 1205 1180 1235 1210 dus) Liquidus 447767.7 363998.3 369457.7 462624.3 380809.7 521552.7 305078.8 Viscosity Sample 414 415 416 417 418 419 420 421 SiO₂ 72.66 71.73 71.46 70.48 71.92 72.68 70.33 71.1 Al₂O₃ 11.13 12.54 12.52 12.58 12.38 11.4 12.53 12.46 B₂O₃ 0.29 0.54 0.51 1.89 0.69 0.19 1.84 1.89 MgO 6.71 5.02 5.37 4.64 4.9 6.41 4.96 4.32 CaO 3.59 5.07 5.04 5.15 5.22 4.1 5.1 5.15 SrO 3.02 1.29 1.27 1.23 1.41 2.16 1.22 1.19 BaO 2.49 3.7 3.71 3.92 3.36 2.95 3.9 3.77 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.420485 1.202552 1.229233 1.187599 1.202746 1.370175 1.211492 1.158106 Annealing 807.4 814.3 811.2 794 810.05 811.7 791.5 798.1 point Young's 84.9 83.8 83.8 82 83.7 84 82.5 82.3 modulus Etch index 18.29531 22.0506 22.48202 24.1505 21.12078 18.52005 24.27848 22.49264 Density 2.592 2.608 2.612 2.604 2.5955 2.595 2.61 2.591 T(200 P) 1705 1689 1685 1678 1698 1708 1668 1688 T(35 kP) 1316 1313 1305 1296 1316 1320 1288 1301 T(liqui- 1275 1190 1185 1150 1205 1270 1140 1150 dus) Liquidus 77925.46 526172.7 493710.8 944151.7 375601.8 93163.61 1021322 1051025 Viscosity Sample 422 423 424 425 426 SiO₂ 70.76 71.42 70.93 71.35 71.18 Al₂O₃ 12.45 12.8 12.48 12.45 12.96 B₂O₃ 1.91 0.97 1.87 2.56 1.73 MgO 4.66 4.85 4.46 3.52 3.75 CaO 5.17 4.85 5.17 5.18 4.8 SrO 1.19 1.63 1.19 1.4 1.19 BaO 3.74 3.38 3.78 3.42 4.26 ZnO 0 0 0 0 0 SnO₂ 0.09 0.07 0.09 0.1 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0 0.01 0.01 0.01 RO/Al₂O₃ 1.185542 1.149219 1.169872 1.085944 1.080247 Annealing 794.4 810.8 798.5 794.1319 805.2 point Young's 82.4 83.2 83.3 80.98138 81.4 modulus Etch index 23.05617 22.23406 22.87568 21.30132 23.45326 Density 2.596 2.598 2.594 2.607 T(200 P) 1682 1695 1678 1696 T(35 kP) 1296 1312 1297 1312 T(liqui- 1150 1250 1150 1220 dus) Liquidus 929795.4 124647.6 946089.9 238329.1 Viscosity 

What is claimed is:
 1. A glass comprising: an annealing temperature greater than or equal to about 785° C.; a Young's modulus greater than or equal to about 81 GPa; a T_(200P) less than or equal to about 1750° C.; a T_(35kP) less than or equal to about 1340° C.; an average surface roughness as measured by atomic force microscopy of less than 0.5 nm; and wherein the glass comprises in mole percent on an oxide basis less than or equal to 2.0 mole percent of the individual concentration of TiO₂, MnO, Fe₂O₃, ZnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, Y₂O₃, La₂O₃, CeO₂, ZrO₂, HfO₂, In₂O₃, Ga₂O₃, Bi₂O₃, GeO₂, PbO, SeO₃, TeO₂, and Gd₂O₃.
 2. The glass of claim 1, wherein the glass comprises greater than zero but less than or equal to 5.0 mole percent of the combined concentration of TiO₂, MnO, Fe₂O₃, ZnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, Y₂O₃, La₂O₃ and CeO₂.
 3. The glass of claim 1, wherein the density is less than or equal to about 2.7 g/cc and the specific modulus is less than about
 34. 4. The glass of claim 3, wherein the specific modulus is between 30 and
 34. 5. The glass of claim 2, wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6.
 6. The glass of claim 1, wherein the T_(200P) less than or equal to about 700° C.
 7. The glass of claim 1, wherein the T_(35kP) less than or equal to about 1310° C.
 8. The glass of claim 1, wherein the glass is substantially free of alkalis.
 9. A liquid crystal display substrate comprising the glass of claim
 1. 10. A glass comprising in mole percent on an oxide basis: SiO₂ 60-80; Al₂O₃ 5-20; B₂O₃ 0-10; MgO 0-20; CaO 0-20; SrO 0-20; BaO 0-20; ZnO 0-20; and wherein the glass comprises in mole percent on an oxide basis less than or equal to 2.0 mole percent of the individual concentration of TiO₂, MnO, Fe₂O₃, ZnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, Y₂O₃, La₂O₃, CeO₂, ZrO₇, HfO₂, In₂O₃, Ga₂O₃, Bi₂O₃, GeO₂, PbO, SeO₃, TeO₂, and Gd₂O₃.
 11. The glass of claim 10, wherein the glass comprises greater than zero but less than or equal to 5.0 mole percent of the combined concentration of TiO₂, MnO, Fe₂O₃, ZnO, Nb₂O₅, MoO₃, Ta₂O₅, WO₃, Y₂O₃, La₂O₃ and CeO₂.
 12. The glass of claim 10, wherein the density is less than or equal to about 2.7 g/cc and the specific modulus is less than about
 34. 13. The glass of claim 10, wherein the specific modulus is between 30 and
 34. 14. The glass of claim 10, wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6.
 15. The glass of claim 10, wherein the T_(200P) less than or equal to about 1700° C.
 16. The glass of claim 10, wherein the T_(35kP) less than or equal to about 1310° C.
 17. The glass of claim 10, wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6, T(ann)>785° C., density <2.7 g/cc, T(200P)<1750° C., T(35 kP)<1340° C., Young's modulus >81 GPa.
 18. The glass of claim 10, wherein the glass is substantially free of alkalis.
 19. A liquid crystal display substrate comprising the glass of claim
 10. 